This paper introduces a supervision and control system for wind-photovoltaic-battery power plants， with a detailed interpretation of related key techniques and main functions of the system. It also illustrates the data acquisition and demonstration program， automatic generation control（AGC） program， and automatic voltage control（AVC） program for wind-photovoltaic-battery power plants. The technological functions have been realized in a national demonstration project of wind-photovoltaic-battery power plant.