The invention discloses a testing task electrical system of a rail-defect detector car. The testing task electrical system comprises a signal analysis and processing module, an electronic cabinet, an electrical controller, a man-machine interaction touch screen, an actuator and a sensor. An ultrasonic signal and a mileage signal from the electronic cabinet and a temperature signal from the sensor are analyzed and processed by the signal analysis and processing module to generate a processing result signal; the electrical controller receives an operating command from the man-machine interaction touch screen and sends the processing result signal output by the signal analysis and processing module to the man-machine interaction touch screen to display at the same time; the signal analysis and processing module outputs the processing result signal to the electrical controller to analyze and process the processing result signal so as to control the actuator to act; and the electrical controller acquires the state information of the actuator, and the man-machine interaction touch screen displays the state information of the actuator. The system disclosed by the invention can solve the technical problems of complicated operation, relatively weak capacity of resisting disturbance and relatively low degree of automation in the existing system.