Within a coordinated fiscal financial policy framework, this study combines complex network analysis with cellular automata to construct a contagion model of debt risk across industrial enterprises. It then uses numerical simulations to examine the dynamic evolution and mitigation strategies of debt risk contagion. The results show that the following: (1) As the contagion probability, immunity failure probability, and contagion probability of immune enterprises increase, debt risk contagion among industrial enterprises is strengthened, whereas higher immunity probability and recovery probability improve network stability. (2) Market noise, carbon tax rate, credit interest rate, and risk preference increase the basic reproduction number relative to the critical boundary of one, whereas fiscal subsidy intensity, green credit ratio, and risk assessment capability reduce it. Within the normalized simulation framework, a carbon tax rate around 0.3, fiscal subsidy intensity around 0.15, and green credit ratio around 0.5 serve as illustrative model-based reference values for interpreting changes in debt risk contagion pressure and risk-mitigation effects. (3) Coordinated fiscal–financial intervention can more effectively reduce $R_0$ and narrow the contagion scope than a single policy tool, suggesting that debt risk prevention should combine fiscal support, green credit allocation, risk assessment improvement, and carbon-policy rhythm management.