As　a　type　of　special　light　source,　microelectronic　mechanical　system　(MEMS)　vertical　cavity　surface　emitting　laser　(VCSELs)　has　the　advantages　such　as　low　power　consumption,　high　modulation　speed,　broad　wavelength　tuning　range　and　easy　coupling,　which　has　been　widely　applied　in　the　field　of　laser　communication.　To　achieve　better　performance　of　the　lasers,　such　as　enlarging　wavelength　tuning　range　and　increasing　polarization　contrast,　optimizing　the　structure　parameters　of　inter　cavity　subwavelength　grating　is　indispensable　to　improve　the　distribution　of　optical　field　and　polarization　output　mode.　In　this　paper,　based　on　effective　medium　theory　(EMT),　the　optimal　values　of　period,　duty　cycle　and　ridge　height　of　subwavelength　grating　are　designed　combining　with　the　theory　of　film　(the　center　wavelength　of　tunable　range　is　850　nm　and　the　grating　material　is　GaAs).　The　impact　of　grating　duty　cycle,　ridge　height　on　the　transmission　efficiency　for　TE　and　TM　are　analyzed.　Furthermore,　the　tuning　ranges　of　MEMS　VCSELs　with　no-etched　grating,　unoptimized　grating　and　optimized　grating　are　compared.　The　results　indicate　that,　for　the　specific　wavelength　tuning　range　and　grating　material,　optimization　of　the　grating　parameters　can　promote　the　increase　of　the　grating　transmission　efficiency　for　TE　or　TM　mode,　enhance　the　coupling　of　optical　field　between　the　semiconductor　cavity　and　air　gap,　thus　enlarge　the　wavelength　tuning　range　of　the　laser.　©　2016,　Chinese　Lasers　Press.　All　right　reserved.