An experimental apparatus based on the differential capillary rise method for measuring the surface tension was built up and verified. The surface tensions of R1234yf and R1234ze(E) were measured from 242 to 365 K and 242 to 380 K, respectively. The surface tension data were correlated as a function of temperature, and the average absolute deviations between the 0-experimental and calculated values were 0.002 mN.m(-1) for R1234yf, and z 80.009 mN.m(-1) for R1234ze(E). The surface tension data at temperature lower than 273 K was first reported.