The shutdown transition process of the motor-pump device was studied by ANSYS Fluent software, which mainly explored the external characteristics and internal flow field in the shutdown process. It was found that the braking condition of the motor-pump accounted for the smallest ratio of the whole shutdown process, the runaway speed was about 84% of the design speed, and the runaway flow rate was 1.17 times of the design flow rate. The flow direction of gap backflow in the shutdown process was always from the impeller outlet to the impeller inlet, and its total flow rate showed a gradually decreasing trend. During the shutdown process, the axial force as a whole showed a decreasing trend;the radial force of the rotor as a whole showed a decreasing trend and then an increasing trend;the pressure pulsation at the impeller inlet and outlet was firstly decreased and then increased, and after reaching the maximum value in the braking condition, it was rapidly decreased in the turbine condition until it entered the runaway condition and stabilized. The impeller inlet pressure pulsation amplitude was the largest in the pumping unit, about twice that of the impeller outlet. Due to the influence of the gap backflow, there was a small vortex in the impeller inlet near the rim area, the range of which was firstly decreased in the pumping condition, then suddenly increased in the braking condition, and finally decreased again in the turbine and runaway conditions. The position of the impeller inlet vortex was gradually moved towards the impeller inlet during the shutdown process. The entropy production within the motor-pump unit was mainly concentrated in the downstream region, headed by the impeller. As the shutdown process progressed, the high entropy production area inside the pump unit was gradually moved towards the inlet guide vane, and the range of the high entropy production area was firstly decreased and then increased. The location and range of the high entropy production region in the pumping section of the motor-pump corresponded to the location and size of the vortex, which indicated that the vortex and the poor flow conditions such as deliquescence were the main reasons for the high entropy production within the pumping section of the motor-pump.