Base　on　three　wave　coupled　equations　and　energy　conservation　law,　the　frequency　doubling　properties　of　CsBe2BO3F2　(CBBF)　are　analyzed　theoretically　at　the　first　time.　The　phase　matching　angle,　effective　nonlinear　coefficient,　walk-off　angle　and　permitted　parameters　are　simulated　in　type　I　and　type　II　phase　matching.　The　difference　of　the　CBBF　optical　properties　between　type-I　and　type-II　are　elucidated.:　a　wider　phase　matching　range,　a　larger　effective　NLO　coefficient　and　a　smaller　walk-off　angle　in　range　of　693.9　similar　to　2730　nm　in　type-I　were　obtained.　The　properties　of　CBBF　have　been　compared　with　the　KBe(2)BO3F(2)　(KBBF)　crystal.　The　larger　lowest　wavelength　limit,　smaller　walk-off　angles,　a　broader　permitted　angle　and　a　larger　peak　value　of　the　permitted　wavelength　of　CBBF　were　proved.