In hydro-generator units, the thrust bearing oil tank has the largest volume and the internal structure is relatively more complex. Therefore, there are many oil mists in the oil tank, and there are often internal and external oil spills, which have a great impact on the safe and stable operation of the unit. Based on the basic theory of computational fluid dynamics, the calculation model of thrust bearing in a power station was established, and the number of pressure oil blade was changed. The ICEM was used to mesh the three-dimensional model, and Fluent was used to calculate. The CFD-POST was used to analyze the oil mist related parameters of thrust bearing oil tank. The results show that in the design of hydro-generator units, the number of pressure oil blade can be appropriately increased, so as to increase the temperature difference between the upper and lower blades, reduce the oil temperature below the blade and increase the pressure, so as to better inhibit the occurrence of internal oil rejection and effectively prevent the diffusion of oil mist due to low pressure.