Abstract: Proper spatial discretization methods and mesh sizes are crucial for the computational accuracy of the discrete ordinates methods applied on the particle transport simulations. Short characteristic spatial discretization splits the computational cell based on the relationship between incoming and outgoing particles, and is capable of mitigating non-physical oscillations caused by the deficiency of the spatial variable discretizing. Exponential short characteristic (EC) is suitable for shielding problems with deep-penetration and strong attenuation, but there are expensive numerical processes including the redundant geometric calculation and nonlinear solving in the previous studies. A modified EC scheme was developed based on 3D structured grids, and the projection mapping was avoided by applying the new splitting-substituting scheme. Optimized exponential moment and exponential factor solving algorithms improve the computational efficiency. From results of four fixed-source problems with simple geometry, accuracy and efficiency were compared among several spatial schemes. The accuracy of EC on the coarse meshes is much better than that of other methods, and its excellent coarse mesh accuracy is cable of compensating the expensive computational cost. Proper mesh distributions help to realize the EC’s advantage of the computational efficiency.