This article analyzes the risk contagion mechanism of local government implicit debt from the perspective of multi-subject collaboration, considering interaction effects among different influencing factors. On this basis, with the help of complex network theory and mean field theory, a risk contagion model of local government implicit debt is constructed, and then the evolution characteristics and control strategies for risk contagion of local government implicit debt are analyzed theoretically and simulated. The main findings obtained from the study are: (1) A scale-free network is not conducive to the risk contagion of local government implicit debt, while the opposite is true for a random network. (2) Information openness accuracy and information disclosure strategy both exhibit a positive “U” shaped relationship with the risk contagion of local government implicit debt. Debt management level, emotional tendency, risk preference level, credit policy robustness, accountability mechanism soundness, and perfection of laws and regulations are all negatively correlated with the risk contagion of local government implicit debt. (3) In order to effectively reduce the risk contagion intensity of local government implicit debt, local governments at all levels should continuously strengthen their debt management capabilities and information openness, and the central government should continuously improve accountability mechanisms, laws, and regulations. At the same time, financial institutions and the media should actively play the role of “stabilizers”. However, the local government implicit debt risk is an inherent risk, and its control focus should be on reducing rather than eliminating the risk.