The invention relates to a preparation method of an aluminum-based boron carbide neutron absorption composite material. The preparation method comprises the following steps of: according to the characteristics of a neutron absorption composite material, grinding, blanking, cold-pressing, baking, hot-pressing raw materials of aluminum powder, silica powder, titanium powder and boron carbide powderby using a powder metallurgic method to prepare the aluminum-based boron carbide neutron absorption composite material in a vacuum state. The tempering quantitative treatment is carried out on the aluminum-based boron carbide neutron absorption composite material so that chemical and physical properties of the aluminum-based boron carbide neutron absorption composite material are more stable. Thepreparation method has the advantages of advanced and reasonable process, continuity and compact, detailed and accurate data, reasonable material proportioning, stable chemical and physical properties and mechanical property and favorable product purity as high as 99.5% and is ideal. Various neutron absorption parts can be prepared by using the aluminum-based boron carbide neutron absorption composite material.