The thermal-stress-induced depolarization is analyzed by numerical simulation in conduction cooled end-pumped YAG slab of finite dimensions with its length along the crystalline ［111］ axes. Simulation results show that the depolarization loss will be underestimated under plane-strain approximation. The alignment of the crystal’s axes with respect to the slab dimensions and the bounce number of the light in zigzag propagation are shown to significantly determine the depolarization loss. It’s not a reasonable solution to increase the bounce number of the light in zigzag propagation for minimizing depolarization loss in spite of the cut angle. Nevertheless, it is feasible for the slab with its width along ［101］ axes and the signal light can not be completely filled with the end of the slab.