A cleavage and passivation process in high vacuum for bars of GaAs semiconductor laser was investigated. The treatment for bars can decrease the facet defect effectively, so as to restrain nonradiative recombination. Measurements on their PL and XPS show that the PL characteristics of the bars on GaAs which are cleaved and passivated in high vacuum are greatly improved than that of the ones cleaved in the air, and also the thickness of the passivation film for vacuum cleavage passivation process is optimized.