The invention discloses a magnitude tracing method for a low-output current sensor. The method comprises the following steps of: cascading a standard current sensor and a current comparator; connecting the primary side of the low-output current sensor and the primary side of the standard current sensor in series; and connecting the secondary side of the low-output current sensor and the secondaryside of the current comparator in series. According to the magnitude tracing method for the low-output current sensor, the method can effectively realize the magnitude tracing of the low-output current sensor.