For　nonlinear　full-state-constrained　systems　with　unmeasured　states,　an　adaptive　output　feedback　control　strategy　is　developed.　The　main　challenge　of　this　article　is　how　to　avoid　that　the　unmeasured　states　exceed　the　constrained　spaces.　To　achieve　a　good　tracking　performance　for　the　considered　systems,　a　stable　state　observer　is　structured　to　estimate　unmeasured　states　which　are　not　available　in　the　control　design.　In　addition,　the　constraints　existing　in　most　practical　engineering　are　the　source　of　reducing　control　performance　and　causing　the　system　instability.　The　main　limitation　of　current　barrier　Lyapunov　functions　is　the　feasibility　conditions　for　intermediate　controllers.　The　nonlinear　mappings　are　used　to　achieve　the　satisfaction　of　full-state　constraints　directly　and　avoid　feasibility　conditions　for　intermediate　controllers.　By　the　Lyapunov　theorem,　the　closed-loop　system　stability　is　proven.　Simulation　results　are　given　to　confirm　the　validity　of　the　developed　strategy.