The rudder force is usually calculated by the empirical formula according to the ship regulations. A more accurate method for calculating the bending moment of the rudder stock has been provided by using the finite element software to calculate the bending moment of the rudder bearing under the rudder stock with the rapid development of science and technology. The direct calculation method approved by the classification society can reduce the calculation value of the rudder stock by comparing with the results calculated by the empirical formula of the classification society. It can improve the accuracy of the design of the rudder system and reduce the construction cost, which has certain value for the shipbuilding industry.