The　edge　emitting　PL　spectrum　of　semiconductor　gain　chip　used　in　vertical　external　cavity　surface　emitting　lasers　was　theoretically　calculated　by　using　Lorenz　linear　function　when　considering　of　the　intraband　relaxation　and　the　valence　band　coupling.　A　model　of　laser　output　which　considered　of　thermal　effect　was　used　to　simulate　our　VECSELs＇　output　power.　The　theoretical　results　were　in　good　agreement　with　the　experimental　results.　The　factors　which　influence　the　output　wavelength　were　discussed　too.