Based　on　the　rate　equation　of　four-level　system　and　numerical　simulation,　the　phase-matching　characteristic　of　laser-diode-pumped　Nd:GdVO4/KBe2BO3F2(KBBF)　solid-state　laser　has　been　studied.　The　influences　of　pumping　and　oscillating　spot　size　to　output　power　and　laser　threshold　with　different　gain　medium　are　studied.　Compared　to　CsLiB6O10　(CLBO)　and　beta-BaB2O4(BBO),　the　phase-matching　characteristics　of　the　nonlinear　optical　crystal　KBBF　are　carried　out　through　numerical　simulation.　For　type　I　and　type　II　phase-matcbing　condition,　KBBF　which　is　more　easy　to　realize　ultraviolet　laser　output　has　more　shorter　transmission　bandwidth　and　more　broader　tunable　phase-matching　angle　than　CLBO　and　BBO.　It　is　useful　to　optimize　and　select　the　parameters　of　such　systems.