Abstract: This paper analyzes two kinds of evaporation in loop heat pipe (LHP) evaporator, namely evaporation at porous wick surface and evaporation in the porous wick. One-dimensional calculation of heat and mass transfer processes is conducted. The results show that evaporation normally takes place at porous wick surface, and evaporation in the porous wick may possibly happen only when inlet liquid is subcooled. Moreover, variables having effects on heat and mass transfer processes are discussed, which include thickness and thermal conductance of porous wick, and sulcool of the inlet liquid.