Abstract: Underwater compressed air energy storage（UCAES） has high energy recovery efficiency（round-trip efficiency） and energy storage density owing to the storage and release of energy at constant pressure and naturally corresponds to offshore wind power in terms of spatial position. To improve its performance, a mathematical model of UCAES describing the process of energy storage and release is built, the key factors affecting the performance are simulated and analyzed, and some technologies for performance improvement are explored. The main research results are as follows: 1) To solve the mathematical model, the highest energy recovery efficiency is taken as the objective function and the mass flow rate of heat recovery media as the decision variable. Subsequently, the optimum mass ratio of air to heat recovery media is determined. 2) To clarify the performance difference between UCAES and tank compressed air energy storage（TCAES）, their working processes are analyzed by comparing them. The results show that the change in tank pressure is the most critical factor affecting performance. Compared with TCAES, the energy recovery efficiency and energy storage density of UCAES increased by 8.25% and 120.82%, respectively. 3) A specific quantitative analysis of the effect of equipment performance and storage depth is performed, showing that improving the efficiency of the expander is more effective in improving the energy recovery efficiency, and depth directly determines the energy storage density. 4) An efficiency improvement technology is proposed and investigated by increasing the expander inlet temperature using electrical energy. The results show that approximately 1/3 of the electrical energy used for electric heating is converted into electrical energy again, and about 60% is converted into available heat energy, which provides a new option for renewable energy heating in the northern coastal city. The results of this study can provide a reference for follow-up project construction, and the promotion of UCAES can provide solid support for the large-scale development of offshore wind power.