Abstract: Air-dried seeds of three tobacco varieties,K326,GuiYan 11 and HongDa,were treated with various doses of γ-ray,different concentrations of NaN₃,and their combinations,the effects of treatments on seed vigor were investigated.The results indicated that γ-ray,NaN₃, γ-ray×NaN₃(interaction effects), γ-ray×variety,NaN₃×variety and γ-ray×NaN₃×variety showed extremely significant effects on seed vigor index.The varieties in the order of sensitiveness to γ-ray treatment were GuiYan11≈HongDa >K326,and the appropriate γ-ray dose was 330 Gy.The varieties in the order of sensitiveness to NaN₃ treatment were HongDa> GuiYan11> K326,and the appropriate NaN₃ concentration was 3.5 to 4.3 mmol/L.The varieties in the order of sensitiveness to combination treatment were HongDa >GuiYan11 >K326,and the injury effects on seed vigor index by γ-ray was higher than that by NaN₃ in combination treatment.