Promoting the multi-functional development of agriculture is the core issue and research hotspot of the global agricultural transformation and the sustainable development of urban areas. The dike pond system is a typically agricultural ecosystem in the Guangdong-Hong Kong-Macau Greater Bay Area (GBA). The purpose of this study is to explore the scale effect of the dike pond's multifunctionality (MFA) and its dynamic mechanism in the GBA. The current research at home and abroad has not paid enough attention to the change of the dike pond's MFA with different scales and its dynamic mechanism. This paper begins with a definition and classification of the dike pond's MFA at different scales. Then it provides a scale effect analysis framework to analyze the dynamic mechanism of evolution of the dike pond's MFA. After that, based on an analysis of land use changes from 1980 to 2017 in the dike pond area, a semi-structured interview with 10 farmers,villagers,village cadres and town leader,and the participatory observation,we find that in the development stage of mulberry (sugarcane)-dike fish-pond system, ecological and social functions of the dike pond is balanced. Between the dike pond and the rural, regional production and life form a virtuous ecological cycle, which breeds the culture of dike pond integrated with rural, regional settlements, industry and society. In the development stage of dike pond based on single culture, rural collective economic organizations and farmers act as the direct beneficiaries of the dike pond production function, one-sided pursuit of economic benefit maximization, leading to the weakening of ecological function of dike pond. The coordinated development of the dike pond's MFA depends on the linkage and cooperation of different scales. It's key to integrate the dike pond's MFA by innovating the land management and coordinating the stakeholders between different scales and the business entities, including strengthening the spatial control of the dike pond development from the national and provincial level in order to maintain its ecological function; implementing shared governance of the region and the rural to promote the functional transformation of the rural side pond (rural center pond); adopting the joint action mechanism of region, rural and farmers to improve the comprehensive benefits of the dike pond's MFA. In the future, we needs to carry out the quantitative evaluation of the multi-functional of the dike pond at the regional level, especially at the level of districts, counties, towns and villages, and further explore how the land use management system affects the multi-functional stakeholders of the dike pond at different scales.