Abstract: The control rod drive mechanism (CRDM) is an important equipment of the nuclear power plant reactor, taking on functions such as reactor startup, power regulating and safe shutdown. In order to ensure the operating conditions of the CRDM, the axial heat transfer experimental and theoretical analyses were carried out. Based on experiments, the inner wall temperature of the driving rod at the height of the coils was measured and the relationship between the heating power and air cooling velocity was established. In addition, the minimum air cooling velocity and the corresponding heat loss were obtained. Based on the theoretical analysis, a heat transfer model was established. The simulation results show good agreement with the experimental data.