Abstract: The graphical analysis as well as numerical calculation has been used to study the effective reflectivity at antireflection coated facets of semiconductor lasers. Due to the wavelength dependence and finite spectral width of the reflection curve, the reflectivity which takes effect is generally higher than the minimum reflectivity claimed. Accounts have also been made on the choice of the wavelength, where the reflectivity is minimized,in order to increase the effectiveness of the antireflection coatings.