The　crystal　structures,　electronic　structures　and　optical　properties　of　Na　doping　zincblende　(ZnS-B3)　system　(Zn(1-x)NaxS　(x=0,　0.0625,　0.125))　were　calculated　by　using　first-principles　calculation　based　on　the　density　functional　theory　(DFT)　within　the　framework　of　generalized　gradient　approximation　(GGA).　The　equilibrium　lattice　constant,　electronic　structure　including　the　density　of　state　and　band　structure　of　Zn(1-x)NaxS　(x=0,　0.0625,　0.125)　were　discussed　in　detail.　The　effects　of　the　electron　configuration　around　Fermi　level　on　optical　properties　of　Na　doped-ZnS　materials　were　analysized　theoretically.　The　calculated　results　revealed　that　Na　doping　played　an　important　role　in　the　optical　properties　of　ZnS-B3.　The　Na2S　doped-ZnS　materials　showed　good　comprehensive　optical　properties　when　the　doping　concentration　of　Na+　ion　was　at　6.25at%,　while　the　concentration　of　effective　negative　charge　increases　when　the　doping　concentration　of　Na+　ion　was　at　12.50at%,　and　the　S3p　electron　stateed　cross　the　Fermi-level　and　transited　to　high　energy　level.　New　dielectric　peak　presented　in　infrared　spectra　with　low　energy　level　and　increased　the　light　absorption　coefficient,　thus　decreased　the　transmission　coefficient　of　ZnS　materials.　Present　calculated　results　agree　considerably　with　the　experiment　results　in　available　literatures.