The application of the waste heat recovery system to recover waste heat from the vehicle engine exhaust gas has been a effective portion of enormous technical efforts to cope with the environmental regulations that have been carried out. The main objective of this paper is to investigate the performance characteristics of the LT loop boiler of the rankine cycle for the engine"s waste heat recovery system. The experimental results demonstrate that the waste heat recovery system is one of the most effective technology to enhance the fuel consumption efficiency. On the boiler component performance test, we could set the boiler inlet condition at the pump outlet condition with the sub-cool temperature of 5℃and the boiler outlet condition with the super-heat temperature of 5℃, respectively, bringing on the engine coolant inlet temperature and flow rate. The evaluation of the heat dissipation and the pressure drop on working fluid were experimented on the boiler inlet pressure of 32.8 bar, at the engine coolant temperature of 100℃, 110℃and the engine coolant flow rate of 10, 15, 20, 25, 30, 40 LPM.