In order to meet the requirements of the latest national standard of motor energy efficiency grade and improve the operation efficiency of the motor, a 55 kW wet submersible motor is taken as an example, and a rotor electromagnetic scheme design method of permanent magnet assisted synchronous reluctance motor (PMASRM) is proposed. Combined with rotor remanufacturing technology, the rotor of traditional submersible induction motor is replaced and transformed into submersible PMASRM. The designed submersible PMASRM has the same stator core structure and winding form as the traditional submersible induction motor, which improves the utilization rate of materials and reduces the manufacturing cost. The finite element method results show that the efficiency of the modified submersible PMASRM is improved effectively compared with the submersible induction motor.