The　conversion　efficiency　of　frequency　doubling　of　the　novel　nonlinear　crystal　CsBe2BO3F2　(CBBF)　in　type-I　and　type-II　is　researched　by　theoretical　calculation.　In　the　simulation,　the　wavelength　of　the　fundamental　wave　is　1064　nm,　and　the　electric　field　distribution　is　the　plane　wave　and　the　Gaussian　approximations.　In　type-I,　the　second　harmonic　generation　(SHG)　conversion　efficiency　increases　monotonously　with　the　growth　of　crystal　length,　and　approaches　a　maximum　value.　The　conversion　value　of　plane　wave　is　100%　and　70%　of　Gaussian.　In　type-II,　the　conversion　efficiency　varies　periodically　under　plane　wave　approximation,　of　which　the　maximum　value　is　78%　and　the　period　is　9.6　cm,　while　the　conversion　efficiency　changes　oscillatory　under　Gaussian　approximation　and　the　maximum　value　is　about　80%.