The utility model discloses a fault positioning system for a multi-segment cable-overhead line hybrid line. The fault positioning system comprises an optical CT and acquisition unit at each joint of the multi-segment cable-overhead line hybrid line, a differential discrimination device on the multi-segment cable-overhead line hybrid line, and CTs and line protection devices on two sides of the line. And the differential discrimination device receives the current signal of the acquisition unit at each joint, and performs differential protection calculation on each section of cable. When the differential judgment device judges that the cable section breaks down, a locking reclosing signal is sent to the protection devices on the two sides of the line. If the protection devices on the two sides of the line judge that the fault occurs in the overhead line section, a reclosing function is started; and if the protection devices on the two sides of the line judge that the fault occurs in thecable section, the reclosing function is locked. According to the technical scheme provided by the utility model, the overall structure is clear and simple, fault section positioning is carried out onthe multi-section cable-overhead line hybrid line according to a mature and reliable differential theory, and the accuracy is high.