Abstract: A semi-smooth newton iterative algorithm was presented to solve the Reynolds equation, where a massconserving cavitation model was considered. In this study, the cavitation problem was treated as a constraint equation, where film pressure and void fraction were complemented nonlinerly. Cavitation equation coupled with Reynolds equation, equilibrium equation and deformation equation were formulated as a system of equations. The algorithm had a high efficiency instead of using multi-iteration which is widely used in relaxed iterative algorithm. It also had a strong convergence property benefited from substituting the linearity between film thickness and pressure into the Reynolds eqaution. Case studies show that this model can be easily applied into EHD analysis, and can be widely used in journal bearing, mechanical face seal and other lubricant issues.