Abstract: A method of calculating voltage and power of large-scaled photovoltaic power plant includes following steps. Environment models of varies locations within the photovoltaic power plant are obtained. A photovoltaic display model is established by establishing a photovoltaic cell model, combining the photovoltaic cell model with the environment models, determining a combination of the environmental data on photovoltaic panels and the photovoltaic cell model, and determining a quantitative relationship between a photovoltaic cell power generation state and photovoltaic environment. An inverter model is obtained by modeling inverters connected to photovoltaic cells. A grid-side model is obtained. An electrical energy and voltage forecast model is constructed by integrated the photovoltaic display model, the inverter model, and the grid-side model.