In order to know nutrients metabolism of Welsh onion during growth and development, the content of soluble sugar, soluble protein and free amino acid of 15 dffferent varieties were analysed. The results showed, changes of soluble sugar in pseudogstem of Welsh onion development were: low-high-low-high. But different variety changed dffferent1y. The content of soluble sugar of varietiesce e from Japan changed insignfficantly. At the harvest time, the content of soluble sugar of Yanzhihong and Tuoxiangucong attained their highest values.Charles of soluble protein in pseudostem of Welsh onion development were: high-low-low-high. One month after field planting, the content of soluble protein pseudostem was highest. Then the content dropped. At he harvest, the content increased again. Changes of soluble protein in leaf were similar with that in pseudostem. The content of free amino acid in pseudostem increased with the growth and development of Welsh onion, and got its highest value at the harvest. But in leaf changes were: low-high-low-high. The content of free anino acid in pseudostem was far high than that of in leaf.