Abstract: Setting surge bin has many advantages for open-pit mine, the most important of them is that it can improve the reliability of the production system. Based on the operation relationship and the transformation laws of the system before the surge bin, the system after the surge bin and the surge bin, we built the reliability model of the system and gave the calculation formula of flexible system. According to the requirements of mining intensity, and utilizing distribution laws of time to repair the system before the surge bin and the system after the surge bin, we get the optimal deposit of materials and residual space in the period of normal system operation.