The utility model discloses a protection device for an isolation knife execution motor of a direct-current power supply system. Including a housing, A current display nixie tube, a state display indicating lamp and a parameter setting button are arranged on a boss on the top surface of the shell, a current sampling end and a fault output end are further arranged on the top surface of one side of the boss of the shell, and the current sampling end and the fault output end are respectively connected with a signal input module on a circuit board inside the shell and a main contact of a fault removal relay. The invention discloses a protection device for an isolation knife execution motor of a direct-current power supply system. Execution of normal operation of motor, a normally-closed contactof the relay KM is cut off by the side mother knife execution motor M through a fault; The current sampling end obtains the normal operation of a power supply, monitors and detects the working current of the motor in real time, displays the working current through the current display nixie tube, and when a short-circuit fault occurs, when the operation current of the execution motor is too large,the normally open point of the fault output end is closed, a coil is cut off to obtain electricity, the normally closed point of the execution motor is opened, and long-time fault operation and equipment damage are avoided.