BaO-Sm2O3-5TiO(2)　(BST)　added　by　Al2O3　was　prepared　by　solid-state　reaction　method.　The　main　phase　is　Ba3.99Sm9.34Ti18O54　of　orthorhombic　tungsten　bronze　structure,　and　the　secondary　phase　is　Ba1.18Al1.90Ti6.09O16　of　tetragonal　structure,　which　has　two　types　of　grains:　one　is　grey　and　cubic,　and　the　other　is　white　and　quasi　rectangular.　Microstructure　was　characterized　by　XRD,　SEM,　and　Raman　spectra.　Micromechanical　properties　of　different　phases　were　assessed　by　nanoindentation　and　micro-scratch　tests　with　Berkovich　indenter.　Volume　fractions　of　different　phases　obtained　by　statistical　analysis　of　grid　indentation　are　in　good　agreement　with　those　obtained　by　XRD　analysis.　Vickers　hardness　method　is　more　appropriate　for　the　determination　of　the　fracture　toughness　of　dielectric　ceramics.　BST　ceramic　without　addition　of　Al2O3　has　better　mechanical　properties　than　BST-A　with　addition　of　Al2O3,　indicating　that　addition　of　Al2O3　impairs　the　micromechanical　properties　of　dielectric　ceramics.