Abstract: ³²Si is the only long lived radio isotope of silicon which generated in small amount through primary or secondary cosmic-ray induced spallation of Ar in the atmosphere.It has very important applications in many aspects such as the research of global biogeochemical sillion cycle and the application in geochronometry in the range of 100—1000a. However, The precise value of its half-life are discrept and this decreased its applications to a great extent. This work measures the half-life of ³²Si by AMS at China Institute of Atomic Energy(CIAE). ³²Si was generated through radiated Mg₂P₂O₇ and SiO₂ sample was prepared according to certain procedure. The sample was divided into two parts,one for AMS measurement and the other for decay rate measurement. Then the absolute ratio of ³²Si/Si was measured by AMS method and its decay rate was measured by liquid scintillation detector.As a result, the half-life of ³²Si is (182±16)a.