Nature reserves are designated areas aimed at protecting biodiversity and ecosystems, playing a crucial role in preserving biological species and their environments. In recent years, with the continuous expansion of urban built-up areas, nature reserves have gradually been encroached upon by artificial light. This study utilizes vector surface data and point data provided by the China Nature R eserve Biological Specimen Resource Sharing Platform. Additionally, the study employs NPP/ VIIRS monthly data from 2012 to 2021, synthesizing it into annual average data, and optimizes data quality through processes such as outlier removal, negative value elimination, noise reduction, and continuity correction. The research methodology primarily focuses on changes in the quantity, level, and intensity of light pollution. Firstly, regarding quantity changes, this study adopts an NPP/VIIRS pixel value of ≤0.33 as the standard for unpolluted areas and uses the maximum pixel value within a reserve to determine whether it is polluted. Data from 2012 to 2021 are analyzed to calculate the annual proportion of nature reserves free from light pollution. Secondly, for level changes, two nighttime light indices are constructed to represent light pollution levels: the first is the Total Nighttime Light (TNL) of all nature reserves nationwide, and the second is the Mean Nighttime Light (NTM) of nature reserves. Finally, for intensity changes, a linear regression trend analysis is applied to assess light pollution trends across all nature reserves, with linear regression models established based on calculated values for each reserve. The findings are as follows. 1) From a regional perspective, nature reserves in the northwest and north China regions experience relatively less light pollution, with Shaanxi, Qinghai, and Shanxi Provinces being the least affected. In contrast, the central-south region shows the most significant light pollution, with Guangdong, Guangxi, and Hainan Provinces having the highest levels. Over the past decade, the number of nature reserves affected by light pollution has increased in most provinces, with only a few remaining stable. Hainan and Guangdong Provinces experienced the most significant changes, each adding 13 affected reserves, while Jiangxi, Liaoning, Hunan, and Sichuan Provinces also saw notable increases. Stable regions fall into two categories: western provinces such as Ningxia Hui Autonomous Region, Qinghai Province and Guizhou Province saw no new light-polluted reserves, while areas like Tianjin maintained stable light environments from 2012 to 2021.2) A quantitative analysis of all nature reserves affected by human-induced light pollution at the national level reveals that TNL increased annually from 2012 to 2017 and stabilized from 2017 to 2021. From 2012 to 2021, the total DN value increased by 120 000, representing a 71.54% growth relative to 2021. Meanwhile, NTM showed an upward trend during the same period, rising from 0.66 in 2012 to 1.21 in 2021, with an increase of 0.55, representing an 83.85% growth relative to 2012. The analysis indicates that both the number of light-polluted nature reserves and NTM have been increasing, suggesting that light pollution is not only expanding in scope but also intensifying in strength.3) Overall, light pollution in nature reservesin the central and eastern regions tends to stabilize, while the western region shows a slow increase, and the northern region experiences a decline. Based on annual light radiation values, the study quantifies changes in the number of nature reserves affected by different levels of light pollution from 2012 to 2021. Among the three levels, the moderate level shows the most rapid growth, indicating that an increasing number of nature reserves in China are being affected by light pollution. The severe level reveals that parts of 227 nature reserves have light environments comparable to urban built-up areas, which could severely damage ecosystems and disrupt biological rhythms.This study evaluates changes in light pollution in China’s nature reserves using time-series-corrected NPP/ VIIRS nighttime light images from 2012 to 2021. Firstly, it quantitatively analyzes nature reserves unaffected by artificial light. Secondly, it establishes nighttime light indices to assess changes in light pollution across national nature reserves. Finally, it classifies light pollution based on light radiation values to analyze hierarchical changes in light pollution within nature reserves. The results provide a scientific basis for more comprehensive control of light pollution in nature reserves and offer critical support for ecological conservation decision-making. Future research will delve deeper into the potential impacts of light pollution on nature reserve ecosystems, including effects on plants, animals, and nocturnal environments, to provide further scientific evidence for ecological protection. By integrating multi-source remote sensing data and ground monitoring data, the precision and reliability of research can be enhanced, offering a more comprehensive understanding of light pollution in nature reserves. Future studies should also consider establishing buffer zones and formulating relevant policies to control and reduce light pollution in nature reserves.