Abstract: A pump-down system containing water ring pumps is a typical variable speed pumping system. For the variable speed pumping system,the pump-down time is always calculated in segments. In order to improve the accuracy of pump-down time,most research focuses on the optimization of pumping models and pumping speed calculation,and there is little research on the segmentation method. In this paper,the segmentation method for the variable pumping speed pumping process is studied. With segments increasing,the convergence performance of calculation results is investigated,and the main influencing factor is analyzed. An auxiliary verification calculation model is established,and a self-adaptive segmented calculation method is designed. Finally,by comparing the calculation results using the regular method and the new method,it is demonstrated that the new method has higher calculation accuracy with fewer segments.