GaAs surface passivation has been studied by S and N mixture plasma met hod for the first time while the radio frequency (RF) power and pressure are adj usted to optimize the passivation effect by photoluminescence (PL) measurement.T he experimental results show that the PL intensity of the passivated sample is 135% higher than that without treatment.This passivation process has been used in 980nm wavelength InGaAs stra ined quantum well (QW) semiconductor laser fabrication,and an obvious increase in facet catastrophic optical damage (COD) p ower can be obtained.