Abstract: Based on the requirement for the high-efficiency heat transfer in the moon day and the blocking of the heat transfer on the moon night, a high-freezing-point axially grooved switch heat pipe is designed by using the octafluorocyclobutane (C₄F₈) as the working medium. The ground experiments are carried out for its heat transfer characteristics at the normal temperature and for its startup mechanism at the (1/6)g gravitation. It is shown that the heat transfer capacity of the heat pipe exceeds 40 W in the working temperature range of 35~55 ℃, with a temperature difference of less than 5 ℃ at 25 W between the evaporation zone and the condensation zone; the temperature difference decreases with the increase of the working temperature under the same amount of the heat transfer; the heat pipe can startup successfully within 90 s with an inclination to the horizontal plane at either 10° or 30°. This type of heat pipes have been applied in the China’s Chang’e-4 lunar probe. The results of the ground thermal balance test and the on-orbit operation show that the heat pipe can achieve an efficient heat transfer under the high temperature working condition during the lunar day period, and with a good insulation as a consequence of the freezing working medium under the low temperature working condition during the lunar night period.