Abstract Heat transfer performance of loop heat pipe (LHP) is tightly related with the wick positioned between its evaporator and compensation chamber. Experiments were carried out to investigate the effects of wick on LHP heat transfer performance. Two wicks, a sintered copper powder wick and a copper mesh wick, were considered for comparison. The former has larger porosity; its pore size spans within a wide range, but smaller than that of the latter. The measured temperature data indicate that the sintered wick LHP starts up faster and operates more stably. The overall thermal resistance of the sintered wick LHP is also slightly lower than that of the mesh wick LHP. Moreover, the sintered wick LHP is found to be able to start up with heat load as low as 5 Watts.