Reduced Cu/ZnO catalyst was synthesized through solid phase grinding of the mixture of oxalic acid, copper nitrate and zinc nitrate, followed by subsequent calcination in N2 atmosphere without further H2 reduction. The catalysts were characterized by various techniques, such as XRD, TG-DTA, TPR and N2O chemisorption. Characterization results suggested that during the calcination in N2, as-ground precursor (oxalate complexes) decomposed to CuO and ZnO, releasing considerable amount of CO, which could be used for in situ reduction of CuO to Cu°. The in situ reduced O/I-Cu/ZnO catalyst was evaluated in CO2 hydrogenation to methanol, which exhibited superior catalytic performance to its counterpart O/H-Cu/ZnO catalyst obtained through conventional H2 reduction. The decomposition of precursor and reduction of CuO happened simultaneously during the calcination in N2, preventing the growth of active Cu0 species and aggregation of catalyst particles, which was inevitable during conventional H2 reduction process. This method is simple and solvent-free, opening a new route to prepare metallic catalysts without further reduction.