The depolarization feature in high power, end-pumped Nd∶YAG slab lasers is studied. The polarization control and depolarization compensation in high power slab laser output are realized with the usage of high power polarizer and 90°quartz rotator, which effectively improves the polarized output power and the uniformity of the near-field light intensity distribution. The experimental results indicate that, via the optimization of depolarization compensation, the output power of linearly polarized laser is increased from 8.7 kW to 9.6 kW, and the depolarization rate is decreased from 30.8% to 3.1%.