The direct synthesis of HCOOH from CO2 is an atomic economic reaction. The development of reliable multiphase catalysts has become a significant hot topic. In order to provide the basis to the precise design of catalysts, the reaction mechanism of CO2 hydrogenation over the FexZr1-xO2 model catalyst was investigated by using density functional theory. Results reveal that the activation energy for H2 decomposition on FexZr1-xO2 is 0.39 eV lower than that of pristine ZrO2. The decomposition of H2 on the surface of the ZrO2 and FexZr1-xO2 catalyst is endothermic and exothermic, respectively. The active H atoms can be stabilized on the FexZr1-xO2 catalyst, which ensure sufficient high activity H atoms for subsequent CO2 hydrogenation. HCOO* or COOH* intermediate can be formed through hydrogenation of CO2. The computational results show that the formation of COOH* is strongly hindered energetically, while HCOO* is more favorable. The HCOO* can be further hydrogenated to HCOOH* or H2COO*. The activation energies for the formation of those two intermediates suggest that formation of H2COO* is unlikely to be achieved at low temperature. The decomposition of HCOOH* into HCO_OH* and hydrogenation of HCOOH* to H2COOH* were also calculated, and the activation energy required is estimated to be 3.52 eV and 2.32 eV, respectively, much higher than that required for the formation of HCOOH*. Therefore, it can be inferred that the most feasible reaction pathway to the hydrogenation of CO2 on the FexZr1-xO2 catalyst is the formation of HCOOH* through HCOO* intermediate. While other products are difficult to be generated at low temperature due to the high activation energy.