This final project discusses the preconditioners of the types (I +S) in applying Gauss-Seidel method to solve the system of linear equation. We show analyti- cally that the convergence of the Gauss-Seidel method with the preconditioner is better than without preconditioner. This final project is a review of the article of Morimoto [Journal of Computational and Applied Mathematics, 234 (201…