The invention relates to a method of increasing residual current low range measurement precision. The method comprises the following steps of through a residual current transformer, sampling a distribution line residual current; carrying out data processing on the sampled residual current so as to acquire a 50mA current signal which has a same frequency and a same phase with the residual current; feeding back the 50mA current signal to an input terminal of the residual current transformer; measuring the residual current in an output linearity area of the residual current transformer; and subtracting 50mA from a measured residual current value so as to acquire a residual current measurement result satisfying a high precision requirement. In the technical scheme, a residual current measurement error is reduced so that low-voltage distribution-network residual current monitoring data is accurate and effective; and because of accurate measurement of the residual current, a three layer protection system of a distribution-network residual current can be effectively cooperated to carry out motion and operate reliably.