Thermodynamic analysis has been employed in this paper to study the effect of capillarity on the interfacial phase change of liquid without surfactant. and a modified expression of phase change rate of liquid without surfactant has been developed. The new expression demonstrates that the capillarity of the concave liquid surface will promote the interfacial vaporization if sufficient heat is exerted oil liquid, and the capillarity of the convex liquid surface will be helpful for increasing the condensation rate from vapor to liquid. The analyses of this paper showed that the newly developed expression is in accordance with practical observations reported in the literature.