Abstract: The operation efficiency of the power system and motor rotor of nuclear-powered submersibles directly determines the performance of submersibles, and the traditional heat dissipation methods can no longer meet the operation requirements of new submersible motors. As an efficient heat dissipation element, heat pipes can achieve excellent heat conduction in a limited space. Rotating heat pipes improve heat dissipation by using centrifugal force to improve working fluid reflow, thereby significantly enhancing thermal performance compared to conventional heat pipes. In this paper, a rotating heat pipe experimental platform was built to meet the experimental requirements of rotating heat pipes of different lengths. According to the requirements of different operating conditions of nuclear-powered submersibles, the rotating heat pipes with a length of 500-1 200 mm were experimentally studied, the temperature was 80-120 ℃, the rotation speed was 100-400 r/min, and the parameters such as thermal resistance, thermal conductivity and axial temperature distribution were analyzed. The experimental results show that with the increase of speed, temperature control and heat pipe length, more heat transfer needs to be promoted to the heat pipe. The axial temperature distribution shows that the adiabatic section provides good thermal insulation, and the condensation section reflects the good heat dissipation capacity, and the rotating heat pipe can obtain a higher equivalent thermal conductivity coefficient by increasing the rotation speed, which can effectively improve the thermal performance of three different lengths of rotating heat pipes from 100 r/min to 400 r/min at the controlled temperature of 120 ℃, the equivalent heat transfer efficiency is increased by 22.2%, 17.6% and 27.4%, respectively. The length of rotating heat pipe is increased from 500 mm to 1 200 mm, and the equivalent thermal resistance is increased by 55%, but the equivalent thermal conductivity is increased by 14.9% due to the increase in the length of the heat pipe, which increases the heat dissipation area. According to the relationship analysis between Nusselt number and rotational Reynolds number, it can be found that the heat pipe is too long, and the reflux capacity of the heat pipe is insufficient at low speed, resulting in a lack of liquid at the hot end, thus reducing the Nusselt number. Although the increase in controlling the temperature leads to a slight increase in the Nusselt number, the extent of the increase is small. This study provides an important experimental basis for the application of rotating heat pipes in submersibles and similar equipment, especially under constrained space and harsh thermal conditions.