The invention provides a method for increasing the sintering density of a ceramic particle enhanced Al-based composite material and belongs to the field of composite materials. Firstly, water serves as a solvent, a boric acid solution with certain concentration is prepared, ceramic particles with certain mass are added to the solution and evenly stirred, and surface-modified ceramic particles are obtained after drying, calcinating and grinding. The ceramic particle enhanced Al-based composite material with the obviously-increased sintering density is prepared through mixing, pressing and sintering processes. In the sintering process, interface bonding is improved, sintering is promoted and the density is increased through reactions of boric oxide (B2O3), an Al base and the ceramic particles or surface oxides of the ceramic particles. When the green body density of the prepared Al-based composite material is 80%, the density obtained after sintering is more than 95%, and the sintering density is increased by more than 15% compared with that of a composite material prepared through unmodified ceramic particles. The method is simple in process and suitable for preparing the high-performance Al-based composite material, and raw materials are abundant and easy to obtain.