Aiming at the problems of high-speed rail brake, such as difficult maintenance and high maintenance cost, an optimization model for periodic preventive maintenance was established. Based on the reliability theory, an improvement factor was introduced to describe the fault rate evolution rule with the lowest cost as an objective function. Taking the failure rate obeying Weibull distribution as an example, the optimal preventive maintenance times of equipments and the relationships between reliability and cost, reliability and improvement factors were obtained by solving the problem with the Matlab instrument. The validity of the model was verified by an example.