The utility model relates to a photovoltaic power plant system efficiency detection device is connected with the photovoltaic power generation station, photovoltaic power generation passes through at the station and public electric wire netting is inserted to the site, the photovoltaic power generation station is including photovoltaic module, detection device includes subassembly environmental parameter test module, power test module and industrial computer, subassembly environmental parameter test module and photovoltaic module are connected, the power testing module connect in and the site to be connected through wireless network and subassembly environmental parameter test module, the industrial computer is connected with the power testing module. Compared with the prior art, the utility model has the advantages of the data acquisition error is little, the measuring accuracy is high, with low costs.