The prilled ammonium dinitramide(ADN)was coated by polyurethane binders(PU)for reducing it's hygroscopicity.The surface appearance and hygroscopicity of ADN after coating were analyzed by SEM and weighing method.Results show that a kind of floccule of PU is formed on the surface of ADN,which makes the hygroscopicity of ADN after coating less than that before coating evidently.When coated ADN is exposed in the atmosphere for 30 days with the RH less than 60%,the hygroscopicity of coated ADN is only 0.136% and does not increase with the increasing of exposure time.The thermoanalysis and mechanical sensitivity test show that the PU has little effect on the melting point,decomposition peak and enthalpy of coated ADN,but makes the mechanical sensitivity of ADN increase.Friction and impact sensitivity of ADN before and after coated are 30%,60%,30.5 cm,and 27.8 cm,respectively.