Aiming at the high reliability and high maintenance cost of the main bearing in the wind turbine, a maintenance optimization model based on the lowest maintenance cost per unit time is proposed. Firstly, by analyzing the vibration signal of the main bearing of the wind turbine, the characteristic value which can reflect the degradation process of the bearing is extracted, and then establish the Weibull proportional hazard model. Secondly, the failure rate curve of the main bearing during the degradation period is analyzed to determine the failure replacement threshold of the main bearing; then improve the traditional failure rate by modifying the traditional agereturn factor, and analyze the model operation results to avoid the phenomenon of undermaintenance during regular maintenance; Finally, determine the maintenance cycle with the best maintenance cost per unit time. Analysis of the maintenance optimization model and the calculation results show that the maintenance cost per unit time can be reduced by 14.4% through model optimization.