The　TD-B3LYP　method　and　the　plane-wave　formalism　of　DFT　method　were　applied　to　predict　the　blue　luminescence　and　nonlinear　optical　effect　of　C-doped　GaN,　respectively.　The　introduction　of　carbon　dopant　will　generate　different　acceptor　or　donor　levels,　which　are　mainly　composed　by　p　electronic　state,　within　the　energy　gap　of　GaN.　Exploring　the　calculated　luminescence　spectra　based　on　the　optimized　excited-state　structure,　C-N:GaN　exhibits　high　luminescence　intensity　and　has　nice　monochromatic　property.　In　addition,　the　corresponding　second-order　nonlinear　optical　coefficients　are　considerable,　chi((2))(xzx)=　-　15.07　pm/V　and　chi((2))(zzz)=26.91　pm/V,　which　are　about　28　times　and　50　times　of　the　second-order　optical　coefficient　of　KDP　crystal.　(C)　2010　Elsevier　Inc.　All　rights　reserved.