China is in the process of establishing and improving the national park system and carrying out pilot projects. With China’s vast territory and diverse ecological systems, appropriate delimitation of the boundaries of national parks is a key scientific issue in the construction of the national park system. Guidelines for the establishment of national parks attach great importance to its cultural service functions such as scientific research, education and public recreation. It is of practical significance to consider the cultural service values of ecosystems when exploring the boundary delimitation methods used to delineate national parks. Based on remote sensing images and network big data resources, this paper selects the Guangdong-Hong Kong-Macao Greater Bay Area as the study area and evaluates the value of ecosystem cultural services in this area. From the perspective of cultural service protection, this paper simulates a variety of scenarios and determines the optimal boundaries through comparative analysis, taking the risk of decision-making into consideration. The principal findings are as follows. (1) Cultural service value varies greatly among regions. (2) Considering the risk and balance of decision-making, seven risk coefficients (0, 0.2, 0.4, 0.5, 0.6, 0.8, 1) between 0 and 1 were considered, and this analysis generated seven scenarios for national park boundaries. (3) Scenario 5 is the most favourable, with cultural, recreational, biodiversity, recuperative and aesthetic cultural efficiency values of 1.292, 1.520, 1.469, 1.543 and 1.430 respectively. This study provides a novel approach for the delineation of national park boundaries, and serves as a reference for regional development planning.