Abstract: Pt/TiO2 catalyst was prepared by microemulsion system of CTAB/butarol/cyclohexane/H2PtCl6 using hydrazine as reductant and TiO2 as support. The effect of microemulsion compositions and the crystalline state of TiO2 on the activities of Pt/TiO2 catalysts for selective hydrogenation was studied using o-chloronitrobenzene (o-CNB) selective hydrogenation as a probe reaction. The results showed that Pt/TiO2 catalyst having the highest activity in selective hydrogenation of o-CNB was prepared from a microemulsion system with mCTAB:mbutarol=3:7, (mCTAB+mbutarol):mcyclohexane=3:7 and the amount of H2PtCl6 solution occupied 3.6% of the total system mass. Furthermore, the study of crystalline states revealed that anatase type TiO2 was helpful to enhance the catalytic activity of Pt/TiO2 catalyst.