Optimizing the operation of thermal power plant auxiliaries can effectively reduce the power consumption rate and improve production efficiency. This paper establishes the optimal operation model for variable-speed pumps and fans, which are the main auxiliaries in thermal power plant. The model is based on the operating characteristics of pumps and fans and considers parallel and series operation. The object is to minimize the power of auxiliaries; the constraints contain the requirements of system flow or head, speed limits, flow limits, power limits and pipeline performance. Because of the complexity of the model, the pumps and fans operating performance curves are transferred to piece-wise linear curves at first, then a new 0-1 variable is introduces to characterize the choice of a different Q-P curve at a different speed. The model has been converted to mixed integer linear programming problem and uses commercial modeling tools to solve. The case is to verify the effectiveness of this method.