The invention relates to a method and a system for testing low-temperature accuracy of a fiber optical current transformer. The method comprises steps: the fiber optical current transformer is placed in a temperature test box, and the temperature range of the temperature test box is set; during a fiber optical current transformer temperature changing process, a temperature sensor acquires temperature signals, the signals are transmitted to an information processing unit, the fiber optical current transformer acquires current signals, and the current signals are transmitted to a transformer calibration device; the transformer calibration device receives standard current signals generated by a standard current transformer, the acquired current signals are calibrated according to the standard current signals, and after error data for the acquired current signals are determined, the error data are transmitted to an information processing unit; the information processing unit analyzes the state of the fiber optical current transformer according to the received temperature signals and the error data, and the state is transmitted to an upper computer; and the upper computer receives information transmitted by the information processing unit, and the information is displayed and stored.