The PD diagnosis of three-phase cross-bonded cable is affected by environment and mutual crosstalk. In order to solve the problem, this paper introduces the PD detection and identification for cross-bonded cable based on vector analysis method. The principle of method is that different PD pulse has different attenuation characteristic. The three-phase amplitude relation diagram (3PARD) is established based on the amplitude relation of three-phase pulse. The diagram is used to distinguish external noise from internal PD signal and separate different PD sources. It can be concluded from the result of theoretical research and on-site test that the method has better feasibility and superiority in PD diagnosis for HV cross-bonded cable and can be effectively applied to the on-site detection and insulation diagnosis.