Due to the stability, efficiency and reliability of the loop heat pipe (lhp) with plate evaporator, it has prominent merit in the cooling of electronic devices. In this paper, a novel lhp without compensation chamber is experimentally studied, and the effect of the location of vapour grooves on the thermal performance of the lhp is analysed, including start-up process, cycle operating performance, temperature distribution and thermal resistance. The results show that the lhp cannot start up thoroughly when heat load is lower than 70w at location b, and the operating temperature is higher than location a. When heat load is over 70w, the lhp start up entirely. When heat load is 150w, the maximum temperature of heating surface and evaporator at location b are 83.3℃ and 63.9℃ respectively, lower than those of location a, which are 86.5℃ and 69.68℃. The infrared thermal image of the lhp shows that the whole temperature of lhp increase with increasing heat load and heat sink temperature. In addition, when heat load is over 100w, the temperature of lhp at location b is lower than that of location a, which indicates the lhp operates better in high-load condition.