Abstract: The rudder shaft in the gap is one of the most severely heated parts of high speed aircrafts. In order to reduce the thermal-protection pressure of rudder shaft, the heat load of rudder shaft is greatly reduced by transferring the high heat flux zone from the rudder shaft to the thermal-protection ring. It effectively realizes the separation of the force load bearing function of rudder shaft and the thermal load bearing function of thermal-protection ring. In this paper, three research aspects were carried out. Firstly, the comparison of thermal environment of rudder shaft with or without thermal-protection ring between simulations and experiments was studied and the results show that the heat flux of rudder shaft can be obviously decreased by using the thermal-protection ring. Secondly, it shows that the way of reducing the thermal environment of rudder shaft is feasible by transferringrudder shaft's high heat flux zone to thermal-protection ring. Thirdly, the influence of rudder deflection on reducing thermal environment of the rudder shaft was studied by analyzing the law of the thermal environment with different rudder deflections.