The connect & off-grid device which meets all sizes of microgrid is developed. This device, which is installed on control center of microgrid, real time collects the three remote information of point of common coupling, distributed generation, and energy storage and load. When receiving the scheduling of master station connect & off-grid command or fault detect, the device coordinates smart devices such as micro electrical protection measurement and control equipment, energy storage inverter and fan inverter, realizing micro grid connect & off-grid switch control. This device has been successfully applied in Luxi island micro power grid demonstration project, which has wide range of application in the future.