In this work, we have studied Susceptible-Infected-Recovered (SIR) model with vital dynamics and constant population, which is used as a mathematical models in many physically significant fields of applied science. The Homotopy Perturbation Method (HPM) and Runge-Kutta method (RK) have been used for solving the SIR model with vital dynamics and constant population. The convergence of HPM has been studied. Also, we have tested the HPM on solving different implementations which are show the efficiency and accuracy of the method. The approximated solutions of HPM for the tested problems are agree well with the numerical solutions of Runge-Kutta method.