In order to improve the efficiency of ocean energy utilization, this paper proposes a self-starting integrated power generation device based on a vertical axis fixed declination hydraulic turbine, and conducts a numerical simulation study of the power output characteristics of the device. Firstly, a three-dimensional two-phase flow numerical pool was constructed using Fluent software, and the mesh partitioning scheme was determined by comparing the difference values of the power output parameters of the device under different mesh densities, and at the same time, the validity of the application of the numerical pool was verified. Secondly, the established numerical pool was used to simulate the change rule of torque, speed and power coefficient of power generation devices in different flow fields under different water wheel blade numbers, radius ratios and height ratios. The results show that the device performs better in terms of torque stability, speed characteristics, and energy utilization in the simulated working condition range when the water wheel blades are 3-4, the radius ratio is 0.25-0.375, and the height ratio is 1/6-1/3. The device is able to start quickly in the presence of wind, and the power coefficient reaches 0.3-0.4 or even exceeds 0.4, with good starting and power generation performance. The research results can provide reference for the design and application of the device.