The global stability of a SIS epidemic model with vaccination and nonlinear incidence rate was investigated. The threshold of epidemic equilibriums-basic reproduction, the number R₀was provided, which determines the extinction or prevalence of the disease. If R₀≤1, the disease gradually disappears. If R₀>1, the infection pesists in its existence andthe disease becomes a local disease. The global asymptotical stabilities of the disease-free equilibrium point and endemic equilibrium point were proved by using the Lyapunov-LaSalle invariant set theory.