With the growing awareness of dual threats of global warming potential (GWP) and ozone depletion potential (ODP), the theoretical analysis and experimental testing of R1234yf refrigerant as alternative to R134a in a heat pump were analyzed. The results show that when the discharge pressure decreases from 1.6 MPa to 0.9 MPa, the heating COP h of R134a and R1234yf heat pumps decreases by 26.97% and 28.78%, respectively. When the evaporation temperature increases from À10 to 10 C, the heating COP h of R134a and R1234yf heat pumps increases by 12.68% and 20.88%. When the cooling water volume flow increases from 0.14m 3 /h to 0.35m 3 /h, the heating COP h of R134a and R1234yf heat pumps increases by 13.07% and 6.56%. When the chilled water volume flow increases from 0.35 to 0.53 m 3 /h, the heating COP h of R134a and R1234yf heat pumps increases by 30.31% and 29.38%.The error of theoretical calculation and experimental testing is between +10% and À15%.