Based　on　the　Gaussian　beam　propagation　theory,　and　combined　with　the　structure　of　the　laser　diode　stack,　the　fast　axis　beam　model　of　the　laser　diode　stacks　was　established.　And　considered　with　the　divergence　angle　and　directional　factor　of　each　diode　laser　array,　the　calculation　for　the　fast　axis　beam　quality　of　the　diode　laser　stacks　was　amended　which　was　finally　verified　by　the　experiment.　The　result　shows　that　compared　with　the　experimental　measurements,　the　calculation　error　of　this　model　is　only　2.14%.　Compared　with　the　ones　before　amending,　which　are　24.16%　and　18.36%,　the　new　calculation　method　is　improved　a　lot　in　accuracy　and　can　reflect　the　fast　axis　beam　quality　of　diode　laser　stacks　more　exactitudly.　©,　2015,　Chinese　Society　of　Astronautics.　All　right　reserved.