The invention provides a binding agent, a polycrystalline cubic boron nitride sintered body and a method for preparing the same. The binding agent comprises metal aluminum, silicon dioxide, silicon carbide, titanium boride, titanium silicide and titanium nitride. The binding agent, the polycrystalline cubic boron nitride sintered body and the method have the advantages that reaction can be carriedout on the metal aluminum and the silicon dioxide to form aluminum oxide and simple silicon substances in sintering procedures, the melting points of the aluminum oxide and the simple silicon substances are far higher than the melting point of the metal aluminum, the simple silicon substances are further excellent in thermal conductivity, accordingly, the shortcomings of metal binding agents andceramic binding agents can be effectively overcome by the aid of the binding agent, the hardness, the toughness and the thermal conductivity of polycrystalline cubic boron nitride can be effectively improved if the binding agent is used in polycrystalline cubic boron nitride sintered body preparation procedures, and the binding agent, the polycrystalline cubic boron nitride sintered body and the method are broad in adaptability.