The invention provides a cable connector fault diagnosing method. The cable connector fault diagnosing method comprises the steps that the temperature of the outer surface of a cable connector and the temperature of a monitoring point (located at the zero potential position of the outer surface of an aluminum protective sleeve or the outer surface of a prefabricated rubber insulating layer) inside the cable connector are monitored in real time; the linear least squares method is used for identifying relevant parameters of cable connector transient state thermal circuit models through the temperatures obtained through real-time monitoring in order to obtain the time constant tau of the first order transient state thermal circuit model and the steady state temperature rise coefficient k of the first order transient state thermal circuit model; and fault diagnose is conducted on the cable connector by the utilization of the identifying result. By means of the cable connector fault diagnosing method, the four common faults of the cable connector can be effectively diagnosed, the defect that in many quality evaluating theories of simplified models, cable heat capacity and the transient state process of cable connector temperature rise are not considered is overcome, the demand for on-line fault monitoring of the cable connector is met, and the stability of system running is improved.