Abstract: Tangshan Iron and steel blast furnace slag were used to prepare CaO-MgO-Si_O2-Al₂O₃ glass ceramics by melting method.And using the differential thermal analysis,X ray diffraction,scanning electron microscopy and other means had been utilized to study the effects of nucleating agents of different types and number of microcrystalline on glass phase composition. XRD results show that the main crystal phase are augite,diopside,diopside aluminum and a small amount of Tschermark’s molecule with addition of 2%Cr₂O₃ as nucleating agent.SEM observations indicates small and irregularly massive grains and high crystallization rate.When 6%Fe₂O₃ is added as nucleating agent,the main crystalline phases are diopside、clinoenstatite and omphacite. The grains are square,triangular and rhombohedral,dispersed in the whole diagram,and the crystallization rate was low. The experimental results provide theoretical support for the preparation of different phase compositions and properties,the composition design and the composition of nucleating agents.