The utility model discloses a preliminary identification test system used for evaluating long-term electrical performance of an extruded insulated direct-current submarine cable system. The preliminary identification test system comprises a pool, a direct-buried area, an analog cable loop, a test cable loop, an analog cable temperature monitoring unit and a test cable temperature monitoring unit. A preliminary identification test system loop stipulates a test object, layout simulation of ocean and transition region installation and simulates cable arrangement, a temperature monitoring system, a thermal cycle voltage test system, a test system and the like. A cable and an accessory included in the extruded insulated direct-current submarine cable system during actual operation are simulated and a representative laying condition and an operation environment are used so as to form a test system loop and carry out a preliminary identification test. A purpose of evaluating long-term reliability of the extruded insulated direct-current submarine cable system is achieved. The system structure is simple and operation is convenient.