The invention provides a binding agent, a cubic boron nitride polycrystalline sintered body and a method for preparing the same. The binding agent comprises metal aluminum, silicon dioxide, metal chromium, titanium boride, titanium diboride, titanium silicide and titanium nitride. The binding agent, the cubic boron nitride polycrystalline sintered body and the method have the advantages that reaction can be carried out on the metal aluminum and the silicon dioxide to form aluminum oxide and simple silicon substances in sintering procedures, chromium nitride or chromium boride can be formed from cubic boron nitride and the metal chromium which is accelerated by the titanium silicide, accordingly, the shortcomings of metal binding agents and ceramic binding agents can be effectively overcomeby 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 cubic boron nitride polycrystalline sintered body preparation procedures, and the binding agent, the cubic boron nitride polycrystalline sintered body and the method are broad in adaptability.