The properties of coatings have been analysed theoretically and experimentally throughout the deposition process of SiO antireflection films on facets of GaAlAs/GaAs laserwith semiconductor power amplification, and with a wavelength of 808 nm. The transmissivities of cavity faces have been increased from 69% and 32. 6% without coatings to above 90% and 80%with coatings. The coupling efficiency of device, output power of laser and operating lifetime have been imp roved.