Using Vidal grape as raw material, the initial concentration of sugar and assimiable nitrogen was 426.96 g/L and 349.49 mg N/L.Icewine fermentation was performed under 18-20 ℃ by adding 250 mg/L commercial nitrogen source and inoculating 0.4 g/L yeast ST into grape juice.The effect of supplementing assimiable nitrogen on fermentation and quality of icewine was studied by measuring physical and chemical indexes in the fermentation process.The results showed that supplementing assimiable nitrogen could speed up sugar consumption and increase the consumption by 3.23%, decrease the consumption of assimilable nitrogen by 10.03%, significantly increase the content of acetic acid, ethanol, higher alcohols and esters by 5.44%, 4.65%, 9.89% and 11.38%, indistinctively affect glycerol accumulation, compared with the control without supplementation.In conclusions, the appropriate supplementation of assimilation nitrogen could affect the parameter changes during icewine fermentation and significantly improve its quality.