Abstract: Raman spectrum was used to characterize the structure of Mo species supported on TiO_2-modified Al_2O_3. For Mo/Al_2O_3 without TiO_2 samples the bands at 325-350 cm~(-1) and 930-940 cm~(-1) assigned as tetrahedral MoO_4~(-2), and the bands at 215 and 950 cm~(-1) as octahedral MoO_6~(-6) can be observed at lower MoO_3 loading, while Al_2(MoO_4)_3 phase and crystalline MoO_3 appeared respectively at 370, 1004 cm~(-1) and 822, 991 cm~(-1) when the amount of MoO_3 was beyond one monolayer dispersion on Al_2O_3 surface. As for Mo/TiO_2-Al_2O_3 samples, only octahedral MoO_6~(-6) and crystalline MoO_3, but no tetrahedral MoO_4~(-2) and Al_2(MoO_4)_3 phases had been detected at low or high MoO_3 loadings, even calcination temperature of the samples raised to 973 K, which reveals that TiO_2 covered on Al_2O_3 can weaken the interaction between MoO_3 and Al_2O_3, and inhibits the formation of Al_2(MoO_4)_3 phase. When a definite amount of CoO added into molybdena samples the bands of crystalline MoO_3 disappeared, suggesting that CoO can effectively promote the dispersion of MoO_3 on the carrier. The presence of CoMoO_4 phase was observed in Al_2O_3 or TiO_2-Al_2O_3 carriers.