With the large-scale photovoltaic power plants and centralized network, more and more new energy grid problem arises. Distributed photovoltaic power plants connected to the grid, and can lead to accidents such as power grid voltage instability occurs at a certain probability. The fundamental reason is the unreliability of distributed photovoltaic power generation. Solar irradiance and ambient temperature caused by the instability of the PV plant output power. In a large number of articles on the basis of theoretical research, combined with practical engineering applications. Proposed short-term power output of photovoltaic power plants forecast an improved model. This paper presents the main prediction model using the input parameter conditions under different conditions, it can lead to different PV power plant output. Combined with a large number of measured data of photovoltaic power plants, the use of rigorous mathematical theory derivation. Simulation results show that the output power of the short-term prediction of photovoltaic power plants proposed in this paper has good reliability and high accuracy.