The invention relates to an electric water shutoff tool for an underground oil well, and relates to the technical field of oilfield underground tools. The electric water shutoff tool includes an upperjoint, an outer barrel, a lower joint, a center tube, a power module, a motor and a valve mechanism, the power module is installed in an annular airtight space surrounded by the upper joint, the lower joint, the outer barrel and the center tube, a window is arranged on the side face of the outer barrel, a stator of the motor is laterally inserted in the window, the stator of the motor and the edge of the window are sealed by a sealing pad, and thus the stator is connected with the outer barrel as a whole; and the stator of the motor is provided with a through hole for installing a rotor of the motor, the rotor of the motor is installed in the through hole, and a power line on the motor is connected with the power module through a plug-in type electrical coupler. According to the electricwater shutoff tool for the underground oil well, the motor is installed without arranging a steel tube, the installation space of the rotor of the motor is further increased, and by increasing the diameter of the rotor of the motor, output torque of the motor is increased.