Abstract: In the face of the repeated impact of the COVID－19，China has entered a new stage of epidemic prevention and control． Under this background，the rational choice of fiscal policy is crucial to stabilize economic development． By introducing service consumption utility shocks in the nonlinear NK－DSGE model with heterogeneous households and firms，this paper quantitatively simulates the impact of the COVID－19 on the macro economy and compares the implementation effects and multiplier effects of various fiscal policies under the impact of the epidemic． The results show that，on the one hand，the COVID－19 pandemic affects the entry and exit of firms through the service sector，which in turn has a negative impact on the macro economy; On the other hand，the COVID－19 has caused an increase in unemployment and the default rate of household loans，and further aggravates financial risks and economic recession．Proactive fiscal policies play a counter－cyclical role in coping with the impact of the epidemic and effectively alleviated the economic recession． By comparing the regulatory effects of increased government purchases，tax cuts and government transfer payments，it is found that in terms of stabilizing household income and promoting consumption growth，the tax reduction policy is most effective to deal with the impact of COVID－19，while in terms of promoting output and employment growth，the fiscal policy of increasing government purchase expenditure is more effective.The research conclusions provide theoretical reference for financial intervention of epidemic prevention and control．

Keywords: COVID－19 epidemic; Fiscal policy; Multiplier effect; Nonlinear NK－DSGE model