Abstract:In this paper, we measured the HCN potential (HCN-p) of 148 sorghum (Sorghum hicolor (L.) Moench) and sudangrass (Sorghum sudanense) varieties and the changes of HCN-P during seedling growth. The results showed that most of the varieties had their HCN-p more than 1000 ppm (94:59%). Among them, 33.11% belonged to 1400–1600 ppm, 22.97% to 1200–1400 ppm, 17.57% to 1000–1200 ppm, and 14.86% to 1600–1800 ppm. The varieties which HCN-p were less than 1000 ppm or higher than 1800 ppm had a little proportion (11.44%). The varieties with the lowest HCN-p were “Xinliang 80” (672 ppm), “sudancao” (753 ppm), “Huangke Sudancao” (856 ppm), “Limuji” (860 ppm), and “MI03” (876 ppm). Those with the highest HCN-p were “Yuanxin lA” (1967 ppm), “Shisanjie” (1904 ppm), “Mi- bangz” (Da Lai (1900 ppm), “7503 A” (1889 ppm), and Mijia Honggaoliang (1883 ppm). Sudangrass had the lowest HCN-p (about 700 ppm), sweet sorghum had higher HCN-p (about 1500 ppm). with the seedling growth, HCN-p reached its highest value in 4-day-old seedling. The first leaf had the highest HCN-p content, the second leaf and sheath had lower and root had the lowest.