The invention provides a DC partial discharge detection device and method for a converter transformer. Detection impedors are simultaneously connected to a valve-side winding and a line-side winding of the converter transformer respectively in series, and impulse voltages of the detection impedors are monitored; if the polarities of detected impulse voltages of the two detection impedors are opposite, it is thought that partial discharge signals exist in the converter transformer; if the polarities of the detected impulse voltages of the two detection impedors are identical, it is thought that external discharge interference signals exist. The invention discloses a DC partial discharge measurement technology for the converter transformer. The DC partial discharge measurement technology fills up the gap in DC partial discharge detection in the prior art, interference from external discharge signals can be effectively eliminated, and the partial discharge signals inside the converter transformer are accurately separated and are further determined in an electric-acoustic combination mode. By means of ultrasonic waves, the generation of the partial discharge signals is further analyzed and determined, and then the accurate positions of the partial discharge signals are detected; through the electric-acoustic combination mode, the detection effectiveness and reliability are high.