By using the Si₃N₄ ceramic porous material as a wick, a cryogenic loop heat pipe prototype which uses ethane as its working fluid is designed. The cool-down and heat transfer performance of the prototype is studied. The experimental results show that this cryogenic loop heat pipe can operate at room temperature and realize cool-down smoothly when 4 W heat is applied on the evaporator. In the cool-down process, the cool-down of the cryogenic loop heat pipe may quicken with the increase of heat power. When the temperature of the evaporator is 190 K, the prototype can transfer 30 W heat stably.