The equivalent beam qualities of GaInP/AlGaInP strained multiple quantum well laser are measured by transforming nonparaxial semiconductor laser beam into paraxial one non-trunctatedly. The beam quality factor in the direction perpendicular to the junction plane is shown to be smaller than unity. Based on the waveguiding mode and nonparaxial vectorial moment theory, the beam qualities are analysed and calculated, which are basically coincided with the experimental results.