Grassroots pilot programs entering the central decision-making agenda is not a spontaneous occurrence but rather the result of meticulous planning and continuous efforts at the grassroots level. The initiative of grass-roots initiatives can drive policy creation, local policy pilot and influence the central decision-making agenda. This article follows the logic of "concept construction - case demonstration - framework generation" to analyze the complete process and mechanism of the pilot program's entry into the central decision-making agenda through grassroots autonomy. Case analysis is supplemented by shadow cases to conduct process analysis and mechanism mining, and the categorization and practical representation of the concept of political momentum are summarized. Based on the case analysis of "Xiaogang Village in Science and Technology field", explores and summarizes the types, characteristics, and functions of four political momentum: consensus momentum, propaganda momentum, alliance momentum, and decision-making influence momentum. It also analyzes the key internal agency mechanisms that enable grassroots pilot policy plans to enter the central decision-making process. The case study found that various types of political momentum embedded in grassroots autonomous policy creation and policy pilot activities have influenced grassroots pilot policy plans to enter the central decision-making agenda through consensus building, expanding influence, gaining recognition, and triggering potential energy. It has constructed a theoretical framework for the role of political momentum in the creation and pilot behavior of grassroots autonomous policies, extracts and enriches the localized expression of Chinese public policy research.