In order to calculate the stirring loss of high oil level immersed lubricated thrust bearing in high speed hydroelectric unit, an approximation formula of stirring loss calculation is deduced according to the geometrical characteristics of the bearing, and the stirring loss is calculated by the approximation formula and numerical simulation method, respectively. With the thrust bearing of a large pumped storage unit, this paper calculates and compares the stirring loss of the thrust bearing under five working conditions with the rotational speeds of 120 r/min,210 r/min,270 r/min,350 r/min, and 500 r/min of the unit. The results show that the stirring loss is proportional to the rotational speed of the bearing; the higher the rotational speed is, the greater the loss is. The effect of the inlet and outlet flow on the stirring loss is neg- ligible. The stirring loss calculated by numerical simulation and approximation formula has a large deviation at low rotational speed, and the calculation deviation of the two is decreased with the increase of rotational speed. The calculation method with the approximation formula can be used to estimate the stirring loss of the thrust bearing for the scheme design, and the numerical simulation method can be further used for the optimum design of the hearing structure and geometrical parameters.