This paper explains the synthesis and characterizations of Poly(aniline) (PANI)/Sb2O3 nano composite by in-situ polymerization method. It was indicated that Sb2O3 itself could catalyze the oxidative polymerization of aniline through its active surface effect. This could be due to the intercalation of PANI chains into the basal spacing of Sb2O3. TGA counseled the thermal stability of PANI. Through FTIR study, the structure of PANI was confirmed. Comparison of polymerized aniline composite with two different initiators was done. HRTEM confirmed the nano size of Sb2O3. The intercalating nature of PANI chains into the basal spacing of Sb2O3 was also tested.