Abstract: A water-to-water high temperature heat pump was fested experimentally in this work. The inlet water temperature of evaporator was 40 ℃ and the inlet and outlet water temperature of condenser were 70 ℃and 80 ℃ respectively. Almost no conveafioual refrigerant is proper for this high temperature working condition. R22/R141b was taken as heat pump working fluid firstly in this work and heat pump’s pressure performance is improved. Even though the highest cooling water temperature was about 80 ℃,the highest pressure was less than 2 5 MPa and compression ratio was less than 8, which could satisfy R22 compressor’s limits. The performance of system was characterized by refrigerant compositions, compressor RPM and water temperature change. It was found that the coefficient of performance reached its maxim of 2 5 when R22’s molar component was about 75%. If only the water temperature difference in evaporator Δ T E increased, the heating and refrigerating capacity all decreasd. However, the heating and refrigerating capacity all increased with water temperature difference in condenser Δ T C. Frequency of compressor had little influence on heat pump’s COP and working fluid’s (R22/R141b) composition if the compositions and working condition remained unchanged.