The invention provides a modeling method for a photovoltaic power generation system model. The method includes the steps: selecting and calculating a photovoltaic power generation system calculation base, and converting a power grid load flow calculation unit value into a photovoltaic power generation system calculation unit value; calculating a transient initial value of a photovoltaic power generation system; building a photovoltaic square array model; and building a grid-connected photovoltaic inverter model. The modeling method is used for modeling a positive sequence component of the photovoltaic power generation system and can be extended into a modeling method for modeling the positive sequence component and a negative sequence component, the model is applied to transient, stable and analytical calculation of a photovoltaic access power grid, and basic model platform support is provided for planning and design of the photovoltaic access power grid and research of the interaction relationship between the photovoltaic access power grid and a power grid.