The purpose of the study is to obtain the hydraulic characteristics of the low-lift pump device during the pump stop transition. The main contents of the research are as follows:the dynamic balance equation of the torque during the transition process of the low-lift pump device; the use of moving least squares to fit the full characteristic curve of the pump; the flow and head balance equation of the fast gate during the closing process. The mathematical model of the transition process is comprehensively obtained. Then, the Matlab simulation module Simulink was used to model the transition process of the low-lift pump installation, and the main hydraulic parameters were simulated. The simulation results show that the established mathematical model of the low-lift pump device during the pump-off transition process is correct, and the Simulink model can be used to facilitate the simulation analysis.