The invention relates to a method for measuring the partial discharge of a joint with an insulation defect, which comprises the following steps of: 1) connecting water pipes with the two ends of the joint with the insulation defect and arranging water terminal equipment at the tail end of each water pipe; 2) arranging a signal leading-out wire on the joint with the insulation defect; 3) applying power frequency high voltage to the water terminal equipment on the two sides, and acquiring a partial discharge signal by using a signal sensor; and 4) outputting the partial discharge signal through the signal leading-out wire. Compared with the prior art, the method has the advantages of effectively judging the insulation condition, preventing the sudden failure of cable equipment, and improving the power supply reliability of a cable system.