During the time between December 1927 and April 1928, with the impacts of “establishing the capital and building a city”, the Nanjing Special Municipal Government quickly launched urban planning strategies with the goal of “building the capital”. As the first planning strategy after the founding of the capital, Capital City Plan had profound influence on the subsequent urban planning of Nanjing, although it is not as well-known as The 1929 Capital Plan. Its planning thought of “inheriting the glory of history and opening up a new scientific situation” made it a key node in the history of modern urban planning in Nanjing.The development of planning is closely related to the establishment of the capital city, the specialisation of administrative agencies, the demarcation of the city area, the mayor’s ideas and the core role of the Special City Public Works Bureau. On 18 April 1927, Nanjing’s administrative status was clearly defined as the “national political and military centre”, and its urban construction was immediately given national symbolic significance. On June 6, the National Government promulgated the “Nanjing Special City Provisional Regulations”, which for the first time stipulated the planning, construction and management functions of the Public Works Bureau in legal form. On 31 March 1928, the first statutory administrative scope of Nanjing Special City was determined, laying a spatial foundation for the development of urban planning. The first mayor Liu Jiwen gave priority to political symbols, and the successor mayor He Minhun emphasised technical rationality. Their complementary governance concepts and the vision of “focusing on the capital” became the guiding ideology of Capital City Plan.According to the intentions of the two mayors and the city government’s policy program, the Public Works Bureau officially launched the city’s planning work on 28 December 1927. Under the leadership of Director Chen Yangjie of the Public Works Bureau, the design team consisting of Li Zongkan, Chief Engineer of the Public Works Bureau, Ma Yiqun, Chief of the Design Section, technicians Tang Ying, Xu Baikui, and assistant engineer Pu Liangchou, worked for three months to complete the planning scheme. The results include the city’s zoning plan and four architectural plans for administrative areas, industrial and commercial areas, school areas, and residential areas.The core content of the plan consists of zoning design and detailed planning. In terms of zoning design, the city’s administrative area is the planning scope, and the functional zones are divided into short-term and long-term, new and old cities, and administrative districts. In terms of detailed planning, an innovative oblique boulevard is proposed to connect Xiaguan and Gulou, and a north-south axis is designed in the administrative district. The grid-type capital functional space is combined with the freestyle urban functional space, reflecting the spatial order characteristics of “integration of Chinese and Western” and “integration of the capital and the city”.Although the plan has limitations such as lack of old city content, natural renewal and patterning, its unique historical value characteristics cannot be ignored. Its main manifestations are: firstly, it is the first and only time that the special municipal government has taken the lead in the planning of the capital; secondly, it breaks through the normal axis of Nanjing’s historical capital, integrates the traditional Chinese sensory axis and the Western visual axis, and forms the concept and exploration of the north-south central axis trunk road space; thirdly, onthe basis of continuing the traffic direction of The 1926 Nanjing Municipal Plan, it cuts the curve and straightens the road, proposes the direction of the oblique straight road and the functional attributes of the boulevard, and becomes the prototype of today’s Zhongshan Road due to the construction of the Sun Yat-sen Mausoleum. The formation of this modern axis marks the transformation and development of Nanjing’s urban spatial structure.Through the newly discovered historical documents, the historical research on the “Capital City Plan” not only corrects the academic community’s single positioning of the 1929 Capital Plan, fills the gap in the research of Nanjing’s planning history from 1927 to 1928, but also reveals the initial role of the 1928 plan in the development of Nanjing’s modern urban planning. The study believes that the “Capital City Plan” is a “continuation and expansion” of Nanjing’s urban planning, and its exploration has both historical reference and theoretical enlightenment significance for contemporary urban planning.