【Objective】 Inorder to clarify the effects of different NaN3 concentrations and treatment time on oat seed germination and seedling growth of oat,and select half lethal dose.【Method】 The seeds of two varieties (Ever- leaf and Qingyongjiu 709) were used as materials. Different NaN3 concentrations (0,5,10,15,20 mmol/L) and treat- ment time (1,2,3 h) were set to analyze the seed germination activity and seedling growth after treatment. 【Result】 The results showed that NaN3 concentration was the main factor affecting oat seed germination and seedling growth. The relative germination rate,relative germination potential and relative germination index of oat seeds de- creased significantly with the increase of NaN3 concentration. When the NaN3 treatment of 10 mmol/(L·1 h),the relative germination rate of Qingyongjiu 709 was 51. 08% and the relative lethal rate was 47. 92%. When treated for 2 h at the same concentration,the relative germination rate of Everleaf was 51. 47% and the relative lethal rate was 48. 53%. When the concentration of NaN3 was greater than 10 mmol/L,the relative mortality of the two varieties was greater than 60%. The seeds completely lost germination ability at the highest concentration (20 mmol/L). NaN3 treatment also significantly inhibited seedling growth. The emergence rate,root length and seedling height of Qingyongjiu 709 were more restricted than that of Everleaf under the same condition.【Conclusion】 The half lethal treatment combinations of Qingyongjiu 709 and Everleaf were 10 mmol/L,1 h and 10 mmol/L,2 h,respectively. Qingyongjiu 709 was more sensitive to NaN3 treatment than Everleaf.