Methanol synthesis from CO/H2 and CO2/H2 was carried out at atmospheric pressure over Cu/ZnO/Al2O3 catalyst. The formation and variation of surface species were recorded by in situ FT-IR spectroscopy. The result revealed that both CO and CO2 can serve as the primary carbon source for methanol synthesis. For CO/H2 feed gas, only HCOOZn was detected; however, for CO2/H2, both HCOO-Zn and HCOO-Cu were observed, and without CH3O-Cu. HCOOZn was the key intermediate. A scheme of methanol synthesis and reverse water-gas shift (RGWS) reaction was proposed.