According to the two stage of subsidy decline and grid parity, a model of system dynamics is constructed. Firstly, based on the analysis of the decline of subsidies in the past few years, it is predicted of the installed capacity, investment willingness and unit installed cost of residential photovoltaic in the process of subsidy decline according to a certain reduction ratio. Then, the development trend of each index after it enters the stage of grid parity is simulated. The simulation results of residential photovoltaic development from 2020 to 2028 are obtained. Finally, an example is used to verify the validity of the model. The example shows that residential photovoltaic will change from subsidy decline to the stage of grid parity in 2022, and it will officially transition from the adaptation stage to the development stage of grid parity access by around 2025.