The　crystal　growth　experiment　of　Nb　:　KTP　crystal　has　been　reported.　The　effect　of　Nb　concentration　and　seed　crystal　on　the　Nb　:　KTP　crystal　growth　has　also　been　studied.　The　type　II　phase-matched　(PM)　second　harmonic　generation　(SHG)　cut-off　wavelength　and　optimal　SHG　PM　angle　of　Nd　:　YAG　1.0642　mu　m　laser　and　Nd　:　YAlO3　1.0795　mu　m　laser　have　been　measured.　It　shows　that　Nb　concentration　has　a　great　effect　on　both　crystal　growth　and　nonlinear　optical　properties.　On　the　one　hand,　Nb　ion　produces　new　problem　in　crystal　growth;　on　the　other　hand,　it　improves　the　nonlinear　optical　properties　and　widens　the　application　of　KTP　crystal.　The　X-ray　powder　diffraction　data　of　7.5　mol%　Nb　:　KTP　are　also　presented.　It　shows　that　the　crystal　structure　of　Nb　:　KTP　has　some　changes　when　Nb　dopes　into　the　crystal,　but　the　change　is　small.　(C)　2000　Elsevier　Science　B.V.　All　rights　reserved.