We　used　density　functional　theory　based　on　the　pseudo-potential　plane　wave　basis　set　to　investigate　the　electronic　structure　of　the　beta-LiAsSe2　crystal　with　a　non-centrosymmetric　structure　and　the　optical　properties.　Our　results　indicate　that　for　the　linear　optical　properties　the　birefringence　of　LiAsSe2　is　very　large　(＞0.5)　in　the　infrared　region.　The　adsorption　ability　and　photoelectric　conversion　efficiency　of　long　wavelength　sunlight　for　LiAsSe2　were　found　to　be　superior　to　those　of　CuInSe2.　Regarding　the　nonlinear　optical　(NLO)　characteristics,　LiAsSe2　showed　a　very　large　NLO　second　harmonic　generation　(SHG)　response　in　the　infrared　region　and　the　SHG　coefficient　(d(33))　of　LiAsSe2　is　about　836.5　pm.V-1.　However,　poor　transmission　of　light　in　the　infrared　region　is　predicted　for　LiAsSe2　compared　to　AgGaSe2.　By　an　analysis　of　the　band　structure,　the　SHG　response　of　the　system　could　be　attributed　to　transitions　from　valence　bands　that　were　mixed　with　contributions　from　Li　to　the　unoccupied　bands　near　the　bottom　of　the　conduction　bands.