As　an　active　region,　the　tensile　strain　GaAs1-xPx　quantum　well　plays　an　important　role　in　the　high　power　semiconductor　laser　diode　with　a　wavelength　of　about　800　nm.　Accompanied　with　the　improved　stability　due　to　the　Al-free　active　region,　the　GaAs1-xPx　quantum　well　laser　also　shows　a　high　level　of　catastrophic　optical　mirror　damage　because　of　the　non-absorbing　window　at　the　facet,　which　is　formed　automatically　by　the　relaxation　of　the　tensile　strain　GaAs1-xPx　material.　On　the　other　side,　the　GaAs1-xPx　quantum　well　laser　can　provide　a　transverse　magnetic　(TM)　polarized　light　source　which　is　important　for　many　solid　state　laser　systems.　However,　the　energy　band　structure　of　the　tensile　strain　GaAs1-xPx　quantum　well　is　more　complicated　than　that　of　the　compressed　or　lattice　matched　quantum　well.　Although　the　light　hole　band　is　on　the　top　of　the　heavy　hole　band　for　the　bulk　tensile　strain　GaAs1-xPx　material,　the　situation　may　be　different　from　the　tensile　strain　GaAs1-xPx　quantum　well,　in　which　the　first　light　hole　subband　lh(1)　can　be　either　on　the　top　of　the　first　heavy　hole　subband　hh(1)　or　reversed,　that　will　cause　the　laser　to　generate　either　TM　or　transverse　electric　(TE)　polarized　light　according　to　the　well　structure.　So　it　is　meaningful　to　optimize　the　tensile　strain　GaAs1-xPx　quantum　well　structure　based　on　the　analysis　of　the　energy　band　structure.　Firstly,　according　to　the　6　x　6　Luttinger-Kohn　theory,　the　energy　band　structure　of　the　tensile　strain　GaAs1-xPx　quantum　well　is　calculated　by　the　finite　difference　method.　The　relationship　between　the　interband　transition　energy　and　the　well　structure　parameters　is　established.　It　is　found　that　the　well　composition　x　and　the　well　width　should　increase　simultaneously,　in　order　to　fix　the　first　subband　transition　wavelength　at　about　800　nm.　Special　attention　is　paid　to　the　808　nm　quantum　well,　the　valence　structures　of　different　well　widths　are　calculated,　the　detailed　analysis　of　the　envelope　function　shows　that　the　top　valence　subband　is　lh(1)　for　wider　well　width,　while　it　is　changed　to　hh(1)　for　narrower　well　width.　Meanwhile,　both　the　TE　and　the　TM　momentum　matrix　element　are　calculated　as　a　function　of　the　transverse　wave　vector　for　the　subband　transition　from　c(1)　to　lh(1),　lh(2),　hh(1)　and　hh(2),　respectively.　Further,　the　threshold　optical　gains　of　different　well　widths　are　simulated　for　808　nm　laser　diode　with　the　tensile　strain　GaAs1-xPx　quantum　well　as　an　active　region,　the　wider　well　width　benefits　the　TM　mode,　while　the　narrower　one　is　favor　of　TE　mode.　Finally,　according　to　the　threshold　carrier　density,　the　relationship　between　the　threshold　current　density　and　the　well　width　is　analyzed　for　808　nm　laser　diode　by　considering　both　the　spontaneous　and　the　Auger　recombination,　an　optimum　combination　of　the　well　width　and　the　well　composition　exists.　For　wider　well　width,　the　threshold　current　density　will　be　higher　because　of　the　high　energy　subband　carrier　filling　effect.　For　narrower　well　width,　the　decrease　of　the　optical　confinement　factor　will　lead　to　the　increase　of　threshold　current　density.