Amid accelerating agricultural green transformation, green-ecology-oriented subsidy policies face dual risks of “green fraud” by agricultural entities and regulatory slackness by local authorities, undermining policy goals. To analyze the role of national audit in risk prevention and policy assurance, this paper develops a tripartite evolutionary game model among audit institutions, local regulators, and agricultural entities, integrated with Cellular Automata and Agent-Based Modeling (CA-ABM) to simulate spatiotemporal strategy dynamics. The findings show: (1) Audit strategy drives system convergence; its decision logic shifts from investigating violations and recovering funds under limited coverage to pursuing public value under full coverage. (2) The audit coverage ceiling exerts a threshold effect on farmer compliance and structurally constrains regulatory compliancegiven a fixed coverage level, risk-oriented spatial allocation outperforms decentralized random inspection, while centralized distribution is least effective. (3) Audit deterrence continuity matters more than single-coverage intensity; excessively long intervals trigger periodic system oscillations, thwarting the eradication of recurrent violations even with a raised coverage ceiling. (4) Single-policy adjustments cannot overcome the evolutionary game's dilemmas-ideal equilibrium requires simultaneously aligned incentives across auditors, regulators, and farmers.