Achieving the “dual carbon” objective is contingent upon the ecological development of agriculture. As the only Science and Technology City in China, evaluating the level of green agricultural development in Mianyang during the 13th Five-Year Plan is of considerable practical importance. Using the entropy weight comprehensive evaluation method, this paper determines the level of green agricultural development in Mianyang by selecting panel data from 2016 to 2020 for Mianyang and its counties (cities and districts) and constructing 15 agricultural green development evaluation indicators from three levels: socioeconomic, scientific and technological progress, and resources and environment. The results indicate that the overall level of green agricultural development in the city of Mianyang is satisfactory, and that the level of green development increased each year from 2016 to 2020, with clear differences in the level of green agricultural development between counties (cities and districts) and numerous factors influencing the development of green agriculture. On this basis, it is proposed that local conditions-specific green agricultural development policies be formulated and implemented in accordance with local conditions to promote the ecological and high-quality development of agriculture by capitalizing on the benefits of a science and technology city, and to assist in achieving the “dual carbon” objective.