The vaporization process of refrigerant flowing through capillary tubes is a thermodynamic non-equilibrium process, which means that there is a vaporization delay phenomenon in this process. How to determine the position of flashing inception is a tricky problem This paper gives a general view of the experiment on the distributions of pressure and temperature for the flashing inception and the method to determine the flashing inception from the experimental data. Based on the results, an analysis of the effect factors on the position of flashing inception and underpressure of vaporization is made to lay a physical foundation for the correlation and the theoretical analysis of the phenomenon.