Abstract: The fault location of submarine cable is the first step of its repair,which effectively guarantees that the follow-up repair work is carried out normally and smoothly. Starting from the trip,a full range of fault location processes of submarine cable,such as fault identification and confirmation,fault pre-location,and underwater accurate positioning are discussed. Methods of protection and traveling wave ranging in remote substation,Fiber Optical Current Transducer and differential protection in terminal station,and kinds of online monitoring systems to identify and confirm submarine cable faults are proposed. In terms of pre-location for fault with low or high resistance of long-distance submarine cables, low-voltage pulse, secondary and multiple pulses, inrush current method,differential pulse method,attenuation method and other predetermined positioning methods are proposed. It is also present and discussed a method to accurately find underwater faults of submarine cables based on the electromagnetic induction principle and Remote Operated Vehicle. The related positioning method was simulated and verified in the test cable and the standby phase of the 500 kV ultra-high voltage long-distance submarine cable of the Hainan Interconnection Project,and the effect is good.