To meet the increasing demand for methyl methacrylate, a series of Fe modified Cs-P/gamma-Al2O3 catalysts were developed through the impregnation method and tested for the aldol condensation of methyl propionate with formaldehyde in a fixed-bed reactor. Through various characterization studies, the physicochemical properties of the catalysts were systematically studied, especially the relationship between the number of the acid sites and catalytic activity. The number of medium acid sites was increased effectively by the addition of Fe, and the catalytic selectivity was improved consequently. Moreover, the reaction conditions were also optimized, and the life span of the optimized catalyst was evaluated. The Cs-P-0.1Fe/gamma-Al2O3 showed excellent reusability during a 260 h lifetime experiment.