Abstract: High-order numerical method is a major hotspot of computational fluid dynamics (CFD), the convergence efficiency is one of the main subjects in the study of high-order numerical method. In this paper, the block lower-upper symmetric Gauss-Seidel (BLU-SGS) implicit algorithm is applied to the fifth-order explicit Weighted Compact Nonlinear Scheme (WCNS-E) to solve the Reynolds-averaged Navier-Stokes (RANS) equations on multi-block structured grids. Two typical test cases, subsonic flows over the NLR7301 two-element airfoil and the three-element trapezoidal wing, are adopted to investigate the convergence efficiency of the BLU-SGS approach. By comparison with the original lower-upper symmetric Gauss-Setdel (LU-SGS) implicit approach, the numerical results indicate that the efficiency of BLU-SGS is much better than that of LU-SGS in low speed flow and different implicit iterative methods have little influence on aerodynamic character, such as the typical velocity profiles for boundary layer and the distribution of pressure coefficent for two typical test cases.