The invention discloses a direct current measuring method for a non-vehicle-mounted charging machine corrector and a direct current measuring system. The method includes steps of sampling and measuring direct current and direct current voltage of a charging machine; optimizing sampling data by applying specific method, and reducing the sampling bias, wherein the sampling data comprises voltage sampling value and current sampling value; performing sampling cycle integral multiple time delay compensation on the instant power by voltage sampling value; performing interpolation algorithm compensation on the instant power by the current sampling value; acquiring accumulated power energy at any moment through the compensated instant power. The system comprises a sampling measuring unit, a sampling processing unit, an instant power compensating unit and an accumulated power energy calculating unit; the sampling measuring unit is used for sampling and measuring the sampling data; the samplingprocessing unit is used for optimizing the sampling data; the instant power compensating unit is used for performing the sampling cycle integral multiple time delay compensation on the instant power by voltage sampling value, and performing interpolation algorithm compensation on the instant power by the current sampling value.