Embodiments of the present invention provide a leakage current fault detection method, device and system. The method comprises the following steps: obtaining leakage current generated in a circuit ateach moment in a preset period of time and total current at each moment in the preset period of time; determining a first function image of the leakage current varying with time according to the leakage current generated in the circuit at each moment in the preset period of time; determining a second function image of the total current varying with time according to the total current of the line at each moment in the preset period of time; determining difference between a change trend of the first function image and a change trend of the second function image according to the first function image and the second function image; and realizing leakage current fault detection by judging whether a leakage current fault exists in the circuit according to the difference. The invention can effectively solve the problem of misoperation or refusal to action existing in a leakage protector.