Underwater compressed air energy storage (UWCAES) is a large-scale energy storage technology that can take advantage of hydro-static pressure in the deep ocean. Integrating the UWCAES into offshore wind power generation can store fluctuate and intermittent wind energy, so that the output power can be smoothed to satisfy the user electricity demand. In this paper, the physical model of the wind power generation and UWCAES integrated system has been built. Based on this model, the optimal nominal working condition has been determined under an ideal charge-store-discharge operation mode with the air storage pressure constraint. Then, in order to expand the working condition range, the air and thermal oil flow rate of UWCAES have been optimized under the variable working condition. Finally, an integrated system of a 3 MW×2 wind power and a 3 MW/45 MWh UWCAES have been tested under the real wind power and the user electricity demand data. Results show that, under the ideal charge-store-discharge operation mode, the integrated system can work within the range of 10% to 120%, and the round-trip efficiency is 48.1%~58.4%. Besides, the operation simulation under the real wind power and user load data also shows that, the integrated system round-trip efficiency is 53.7%, and the wind curtailment rate is declined to 0.58% and the load satisfaction ratio is promoted to 99.57%.