Abstract: The electromagnetic scattering from multi-region targets with homogeneous dielectrics and metals are of significant importance in various microwave applications from antenna design to radar imaging. Aiming at the multi-region target scattering problems, the discontinuous Galerkin(GD) solution in the surface integral equation(SIE) method of moment(MoM) is studied, and an optimized distance sparse preconditioner(O-DSP) is proposed. Based on the different matrix characteristics associated with different integrodifferential operators, the proposed preconditioner is constructed by adopting customized sparse strategies, and the sparsity of the preconditioner is further improved. Numerical studies demonstrate that, compared with the conventional DSP, the number of nonzero elements in the proposed precondition matrix is nearly halved, while maintaining similar convergence rate.