Abstract:This research is conducted to study the HCN-p of several types of sorghum, as well as their changes in amino acid. The HCN-p of sorghum seedling reached its maximum in 4–6 days after germination. It was found that the first leaf of the seedling has the highest HCN-p. Among the 14 varieties studied, Atlas had the highest HCN-p (1984ppm), whereas NP-22 had the lowest value (479ppm). Light-grown seedlings had higher HCN-p. There was no obvious difference in protein amino acid in sorghum seedlings with .different HCN-p. However, the free amino acid content did vary in the sorghum varieties. The content of free tyrval, pheleu and ileu in etiolated Atlas seedlings was significantly higher than that in NP-22 seedlings. However, under condition of light, the five free amino acids lowers significantly in content in Atlas when compared be NP-22. This proves that Atlas had a more sensitive enzyme system and under presence of light, its free amino acid content was rapidly converted to cyanide.