This study was performed to get the optimal operating conditions of an water-air compact heat pump system using R-134a. The experiments was done for three elvels of the air mass flow rate and the compressor driving speed during air-heating process. The temperature of the air at the condenser inlet and outlet was 17~23$^{circ}C$, 36~44$^{circ}C$, respectively. The average temperature of the refrigerant at the evaporator and condenser was 1$0^{circ}C$, 6$0^{circ}C$, respectively. The temperature of the refrigerant was not depending on the air mass flow rate and the compressor driving speed. The pressure of the refrigerant at the condenser inlet and outlet was ranged of 10~18.5kg/$ extrm{cm}^2$ and that at the evaporator was ranged of 3.1~3.3kg/$ extrm{cm}^2$. The pressure drop at the condenser and evaporator was about 1.5, 1.2 kg/$ extrm{cm}^2$, respectively. The performance of coefficient for air heating was about 3.3~4.0.