The　transfer　matrix　method　is　used　to　obtain　the　intrinsic　equation　of　the　optical　field　within　the　vertical　cavity　surface　emitting　lasers　(VCSELs),　which　is　solved　by　the　shooting　method.　Numerical　results　show　that　the　method　is　fast　and　precise.　Meanwhile,　the　effects　of　the　GaAs　barrier　thickness　and　the　Al　composition　in　the　spacer　layer　on　the　threshold　gain,　the　optical　confined　factor　and　the　resonant　wavelength　are　analyzed　by　the　method.