The complementation of hydrogen storage and ice storage is promising for improving the energy efficiency of island microgrids. However, there are few types of research on the size optimization of microgrids with the hydrogen-ice hybrid storage. To that end, this paper presents a method for the sizing of wind turbines, PV, diesel generators, hydrogen storage, and ice storage for an island microgrid. The objective of the optimization is to minimize the cost of energy (COE) where the limitation of energy surplus rate (ESR), the loss of power supply possibility (LPSP), and CO 2 emissions are considered. Given the high complexity of the model, a derivative-free optimization technology, Tunicate Swarm Algorithm (TSA), is used to solve the problem. The proposed method is applied to determine the optimum size of an island microgrid on Dachen Island, Taizhou, Zhejiang, China. The simulation results show that compared with hydrogen storage only and ice storage only, the hydrogen-ice hybrid storage has a more compelling performance in improving the economy, reliability, and environmental protection of the island microgrid.