The　interplay　between　minority　and　majority　carriers　in　a　narrow　bandgap　semiconductor　can　benefit　their　thermoelectric　performance.　Herein,　the　optimistic　infiuence　of　in-situ　nanocompositing　in　adjusting　the　balance　between　majority　and　minority　carriers　for　the　p-type　BixSb2-xTe3　thermoelectric　(TE)　material　is　reported.　A　two-fold　strategy　of　grain　refinement　via　optimized　heat　treatment　and　nanocompositing　via　nanosized　Te　addition　for　BixSb2-xTe3　is　explored.　In　the　present　homo-structural　nanocomposite　system,　enhancement　in　power　factor　(PF)　is　benefited　from　the　synergistic　improvement　in　electrical　conductivity　(sigma)　and　the　Seebeck　coefficient　(S).　Further,　experimental　and　theoretical　work　illustrates　that　adjusting　the　antisite　defects　formation　enlarges　the　bandgap　and　fiattens　the　valence　band　edge,　thereby　increasing　the　Seebeck　coefficient.　Conse-quently,　a　high　maximum　figure　of　merit　ZTmax　of　1.46　is　realized　at　operative　temperature　T　similar　to　370　K　(with　Te　content　y　=　4.0　wt%).　These　findings　highlight　the　optimization　of　the　heating　process　and　the　effectiveness　of　the　optimal　in-situ　nanocompositing　that　can　play　a　significant　role　in　developing　atomistic　doping-induced　nanocompositing　based　TE　systems.