Abstract: The electricity consumption of mine multi-level relay drainage system is very large, in order to improve economy of drainage system operation, it is necessary to optimize drainage system control, but current optimal control methods of mine multi-level relay drainage system have some problems such as easy overflow of sump and frequent start and stop of water pump. For the above problems, an optimal control strategy of mine multi-level relay drainage system was proposed. The optimal control model of mine multi-level relay drainage system was established which took water level of each level sump must be between the lowest and highest level and displacement of each level sump should not be less than inflow as constraint conditions, and the lowest sum of electricity costs of each level within one drainage period as objective function. By introducing margin into flow constraint condition, frequent start and stop of water pump is avoided. Gray model is used to predict water inflow, so as to obtain accurate water level of sump and avoid overflow accident. The application results show that the optimal control strategy can reduce electricity cost of drainage system under premise of ensuring safety of drainage.