The strategy of coordinated regional development is one of the major national strategies of the new era, aimed at building a regional economic layout and territorial spatial system with complementary advantages and high-quality development. In recent years, regional cooperation planning programs have been introduced across China, effectively enhancing the wholeness and coordination of the regional economy. However, under the influence of modern western “individual rationality” epistemology, regional cooperation can easily fall into the “Prisoner’s Dilemma”, resulting in problems such as the lack of good implementation of the plan, the lack of systematic implementation of the plan, and the lack of focus in the implementation of the plan. As a result, the study introduces the relationship theory of social sciences to analyze the logic behind the implementation of regional cooperation planning, in order to enrich the research on the implementation of regional cooperation planning in China.Borrowing the core concept of relationship theory “the world is composed of relationships, and any actor is an actor in a relationship”, it can be deduced that the essence of regional cooperation is the game of interests between different subjects. Regional cooperation relations include three stages: “obtaining minimal consensus, establishing relations and initiating cooperation”, “carrying out joint discussions and construction, maintaining relations and sustaining cooperation”, “forming interconnections, developing relations and deepening cooperation”. This process continuously advances the intimacy of the cooperation subjects. On this basis, it proposes the “three-definition “pathway of regional co-operation planning and implementation from a planning perspective. Firstly, defining guidelines. Following the path of "building a consultation platform - clarifying common interests - agreeing on co-operation goals", to enhance the awareness of cooperation among different subjects, and thus strengthen the intimacy of the relationship. Secondly, defining projects. Following the path of “developing action plansidentifying demonstration projects-implementing land security”, to deepen cooperation and enhance the stability of the relationship. Thirdly, defining standards. Following the path of “agreeing on standard principles-negotiating standard norms-linking to statutory planning”, to enhance the depth and breadth of the relationship.