The invention discloses a catalyst for an aldol condensation reaction as well as a preparation method and application of the catalyst. The catalyst includes an active component, an active auxiliary agent and a carrier, the active component is Cs, the carrier is an acid-treated modified SiO2 carrier, and the active auxiliary agent is one or more selected from the group consisting of P, V, W, Sn, B,Bi, Nb, Ba, La, Ti, Al, Sb, Ce, Zr and Fe. The preparation method comprises the following steps: performing acid treatment on SiO2 powder to obtain the acid-treated modified SiO2 carrier; supportingthe active component and an active auxiliary agent on the acid-treated modified SiO2 carrier to obtain a raw powder catalyst; and performing tabletting on the raw powder catalyst mixed with a shapingauxiliary agent to form a shaped catalyst, drying the shaped catalyst, and performing calcination to obtain the catalyst product. The catalyst is used for the condensation reaction of methyl acetate or methyl propionate with formaldehyde; and the yield of the product prepared by using the catalyst provided by the invention is higher, the costs of product separation can be significantly reduced, and the catalyst has higher industrial application value.