Abstract: Three cultivars， Zhenong No.6 （high sucrose content）， Liaoxian No.1 （middle sucrose content） and Xiafeng 2008 （low sucrose content） were used to investigate the sucrose accumulation and enzyme activities involved in its metabolism in developing seeds of vegetable soybean. The results showed that the growth curves of vegetable soybean seeds showed single sigmoid pattern. The change trends of sucrose metabolism among three cultivars were similar. During the whole periods of vegetable soybean seeds development， sucrose was the major component of soluble sugar， taking about 70% of total soluble sugar contents. The net activities of sucrose\|metabolizing enzymes were the major factor affecting sucrose accumulation. During the early stage of seed development， net activities of sucrose\|metabolizing enzymes were negative value. Sucrose metabolism is in the decomposition direction， when sucrose synthase and acid invertase were key enzymes in sucrose decomposition. However， the net activities of sucrose\|metabolizing enzymes turned to positive value in the middle stage of seed development. Sucrose metabolism was in the synthesis direction， when sucrose synthase and sucrose phosphate synthase were key enzymes in sucrose synthesis. During the late stage of seed development， also the net activities of sucrose\|metabolizing enzymes were positive value， but its value was close to zero， showing that the rate of sucrose decomposition and synthesis was similar and sucrose synthase， sucrose phosphate synthase， acid invertase and neutral invertase played a leading role in sucrose metabolism in this stage．

Key words: vegetable soybean, seed development, sucrose metabolism, net activity