This paper studies the influence of the discharge point depth on the ultrasonic detection results of partial discharge in cable terminals to find an effective method to analyze discharge position and discharge level according to the results of cable terminal discharge ultrasonic signal field test. With ultrasonic wave propagation and attenuation theory, this paper analyzes the tangential and longitudinal distribution pattern of discharge signals in cable terminal surface and puts forward a calculation method about the true depth and discharge level of partial discharge source on the cable terminal by the way of theory analysis, simulated calculation, laboratory test and field application. The result reveals that the detected ultrasonic signal level decreases as the axial distance or the central separation angle between the discharge point and the test point increases, and the depth of discharge point influences the change rate of the detected ultrasonic signal level along with the axial distance and the central separation angle. The lower depth means the larger change rate and the higher depth means the less change rate. It’s also revealed that the measured discharge point depth and discharge level by the proposed iteration method are consistent with real situation.