Abstract: A pseudo time iteration lower-upper symmetric-Gauss-Seidel (LU-SGS) method for solving supersonic multi-species chemical reaction flow was introduced. When solving parabolized Navier-Stokes (PNS) equations by space marching method,the modified LU-SGS method was used in the marching plane until reaching convergence. This plane's results were transferred to next plane and the entire flow field was solved plane by plane. Using pseudo time iteration LU-SGS method to solve the chemical reaction PNS equation,the result has the same level of accuracy compared with those obtained from Navier-Stokes (N-S) equations solved by time iteration method,and the computation efficiency is improved to an order or more.