A slip rate detection method and a detection system for detecting the slip rate of an electric vehicle using the method. The slip rate of an electric vehicle is measured by measuring the motor voltage, motor current, and motor rotational speed of the drive motor. The detection system includes a motor rotational speed detection unit, a motor voltage detection unit, and a motor current detection unit, all connected to the drive motor. The motor rotational speed detection unit, the motor voltage detection unit, and the motor current detection unit are connected to a slip rate calculation unit by means of a motor rotational speed signal processing unit, a voltage signal processing unit, and a current signal processing unit, respectively. The slip rate calculation unit is configured with a slip rate calculation formula. The formula is determined according to the drive motor type.