At room temperature micro-photoluminescence spectra of the low Al composition AlxGa1-xAs was tested by laser micro-photoluminescence spectroscopy．The characteristic of photoluminescence test method was studied，and combining with experience calculate expressions of the low Al composition in literature，independent development VB application program for spectra data processing and Al composition calculate has entered on practicality now．The results show that exploiture and application of program is an important characterization instrument for obtaining a Al composition of low Al composition AlxGa1-xAs materials，and provides direction for study and optimization growth technology of AlxGa1-xAs materials，and it has become a important gist for filter eligible materials in making device technology．