The oil film have many excellences such as bigger load bearing capacity, longer life, wider velocity range, lower friction etc. The traditional design method is experience test. Even the design parameters could meet the application requirements, but they can not exert the best performance of the oil film bearing. The relationship between load bearing capacity and materials, lubricants, design parameters and structural characteristics of oil film bearing was analysed. To improve the load capacity and run at the optimal state, the objective function was built to optimize the main parameters. Optimization results showed that the load bearing capacity has been greatly improved.