A security monitoring system for an electric vehicle and a monitoring method thereof are provided. The security monitoring system comprises a security monitor (1). The security monitor (1) receives signals from an accelerator pedal position sensor (5), a motor rotational speed sensor (7), a motor bus voltage sensor (8) and a motor current sensor (6) of the vehicle and outputs control signals to the enable pin of a motor driver (3) and the control pin of a switching circuit (12) respectively. A switch controlled by the signal of the control pin is connected in series between the input pin and the output pin of said switching circuit (12), both of which are connected in series in the input circuit of a relay (4) for controlling the on/off of the power supply circuit for a power battery (11). The security monitor obtains the required torque or power of the vehicle and the actual output torque or power of the vehicle according to information such as accelerator pedal position, motor rotational speed, motor bus voltage and motor current. When the torque or power of the vehicle exceeds requirement, a driving motor is shut down and the power supply circuit for the power battery (11) is cut off, thus ensuring the security of the vehicle.
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