An experimental study of the metastable flow of non-azeotropic refrigerant mixtures R22/R142b through capillary tubes is reported. The temperatures and pressures along capillary tubes were measured in different working conditions and different mixing proportions. Thermodynamic properties were calculated with mixing rules. The quantitative law of metastable flow was shown in the figures. The result shows that the metastable flow phenomenon still exists when non-azeotropic refrigerant mixtwres are used. At the same time, the authors propose that it is necessary to analyse the metastable flow phenomenon theoretically which appears in the process of vaporision of non-azeotropic refrigerant mixtures through the capillary tubes.