The utility model discloses a DC cable partial discharge detection device, and relates to the technical field of partial discharge on-site detection. At present, no perfect detection device exists forpartial discharge of a high-voltage cable under direct-current voltage, and no corresponding standard or special measuring instrument exists. The device comprises a high-voltage direct-current outputdevice, a load current superposition device, a first terminal, a second terminal, a wire connecting the first terminal and the second terminal, a direct-current partial discharge measuring device used for detecting partial discharge signals of a measured cable, a temperature measuring device used for detecting the temperature of the measured cable, and a joint arranged in the middle of the measured cable. And the direct-current partial discharge measuring device and the temperature measuring device are respectively arranged on measured cables on two sides of the joint. Rated load current is applied to a cable loop, so that partial discharge detection for insulation defects of the high-voltage cable under direct-current voltage is effectively realized.