As a new technology to alleviate energy crisis and environmental pollution, producing hydrogen by water electrolysis using wind and solar energy is becoming popular recently. However, due to the randomness and intermittence of renewable energy, the slow dynamic response, the limitation of input power of the electrolyzer for hydrogen production and so on, new operation control technology has to be used to coordinate the sources and loads. In this paper, a simple and optimized operation control strategy is proposed for the wind-solar-energy storage-dominated islanded microgrid used for hydrogen production. The optimal operation is realized by simply regulating the AC-bus voltage of the microgrid system and the operation principle is elaborated on first. Afterward, a simulation model, which includes 2MW wind turbine, 375kW PV system, 315kW energy storage system, 24.2kW PEM and 785.2kW alkaline electrolyzer is established. The validity of the proposed method is verified by simulation results.