Abstract: Influence of cleaning process on laser-induced damage threshold of polarizers was studied. Nomarski microscope was used to inspect the cleaned substrate surface, scanning electron microscope combined with focus ion beam technologies were used to characterize the damage morphologies of polarizer. The initiators that trigger laser damage were correlated with cleaning process. Proper cleaning process resulted in fewer residual particles and nodules in the prepared polarizer, which increased the laser induced damage threshold (LIDT) for S-polarization. Moreover, absorption peak of substrates became lower and sharper when surface contaminations were removed, which improved the LIDT of P-polarization. In conclusion, cleaning is an effective way to increase LIDT of polarizers.