The purpose of this study is to calculate the reliability of the mechanical sand washing system. The basic principle and process flow of the sand washing system are introduced. According to the structural characteristic of the sand washing system, the simplified reliability model of the system is established. Based on the reliability model, the mathematical model of the system reliability is constructed. In the reliability analysis, the curve of system reliability is obtained. The results show that the maximum reliability of the system is approximate 0.9, and the average life of the system is about 5.59 years.