At present, taking a monolithic approach of high frequency current transformer (HFCT) method or ultra high frequency (UHF) method is susceptible for partial discharge detection in the power cable. Joint detection of HFCT method and UHF method is used to improve the effectiveness and accuracy of cable partial discharge detection. In the joint method, the impulse interference is removed by analyzing the simultaneity of two detection results of the pulse signal. The built-in sensor in UHF method cannot be applied to measure partial discharge of the cable in operation, so the external sensor is presented in this paper. In the process of using external sensor, the signal intensity has great attenuation after radiation out of cable joint and propagation in the air. For 110kV three-phase cross-bonded cable, the shield of cable joint is disconnected. Considering that, electromagnetic simulation is conducted to verify the feasibility of using external sensor and find the optimal placement. Finally, the sensors are used in on-site detection. The simulation results are proved to be valid and the joint detection is able to identify the interference signal and real partial discharge signal.