Abstract: The transmissivity and reflectivity of polarized light through Nd-glass are analyzed based on the Fresnel formula. The influence of the off-axis light in high power solid-laser facility on the isolation performance of main-amplifier system is discussed. The attitude of crystal in the small electro-optical switch is adjusted to compensate the depolarization loss due to beam rotating error,according to the mechanism that the off-axis light through the crystal of the switch will result in depolarization loss. Experimental results indicate that the system selectivity towards polarized light is not influenced by the small angle change of Nd-glass, and the isolation rate of main-amplifier system can be improved more than three times through the attitude adjustment.