In order to study the role of printed circuit board(PCB) in high-power LED heat dissipation, a simple model of high-power LED lamp was designed. According to this lamp model, some thermal performances such as thermal resistances of four types of PCB and the changes of LED junction temperature were tested under three different working currents. The obtained results indicate that LED junction temperature can not be lowered significantly with the decreasing thermal resistance of PCB. However, PCB with low thermal resistance can be matched with smaller volume heat sink, so it is hopeful to reduce the size, weight and cost of LED lamp.