Hydrogen-oxygen Regenerative Fuel Cell (RFC) is a kind of energy storage plant, which is suitable for satellite and space station especially. A RFC acts as electric battery and shifts energy from the lightside of the orbit to the nightside. It consists of a fuel cell subsystem and an electrolyzer subsystem. During power drawing operations, a fuel cell generates energy by combining hydrogen and oxygen gas to form water. During charging operations, an electrolyzer is used to covert water back into its constituent part, hydrogen and oxygen. Comparing with other RFC systems, Proton Exchange Membrane Regenerative Fuel Cell (PEMRFC) has many advantages, such as, solid non-corrosive electrolyte, low temperature operation, rapid start up, high power density, simple design, and ease of manufacture etc. In this paper, a lOOw H₂/O₂PEM RFC system in lab is presented. It consists of RFC stack, water-circulating loop, and the supply and the storage for hydrogen and oxygen. Water management is very important for RFC, where water should function as both reactant and product, so keeping balance and recoverable for water is necessary. For this purpose, we design FC stack with passive water removal [1], and adopt a special gas-liquid separator, which needn´t depending on gravity to separate gas and water and suitable for weightless space application. The RFC stack and system gives a good performance in 50-cycle test.