Criminal Policy and Crime Prevention Mechanism: The Role and Effectiveness Evaluation of Criminal Law in Public Security Management

China's public security faces increasingly complex challenges, especially the high incidence of minor crimes, ambiguous criminal behavior, and the emergence of a public opinion focus. The purpose of this study was to explore the role of criminal law in modern public security management, evaluate its effectiveness in preventing crime, and explore the synergy between criminal law and other social governance mechanisms. This article systematically sorts out the evolution, functional positioning, and modern transformation logic of criminal policy, focusing on the deterrent function and boundaries of legal application in public security management. Ccombined with the practical cases of Shenzhen's "criminal-governance-society" collaborative system, the successful experience of this model in improving the effectiveness of public security management and reducing the recidivism rate was analyzed. The study concluded that criminal law plays a key role in preventing crime, but it still faces challenges in the fields of the special prevention and resocialization of released prisoners. To improve the effectiveness of criminal law, we should focus on building a systematic mechanism for the governance of minor crimes, promote the development of alternative punishment and restorative justice, and strengthen the coordination between criminal law, administrative law enforcement, and social services. This will provide a more robust legal guarantee for achieving long-term social stability.