To clarify the effect of Aphis craccivora Koch infestation on the nutrients and protective enzymes of mung bean resistant and susceptible varieties,the contents of nutrients and protective enzyme activities in the leaves of mung bean resistant and susceptible varieties infested by Aphis craccivora Koch were determined,respectively,using biochemical methods.The results showed that after the resistant and susceptible varieties were infested by Aphis craccivora Koch,the soluble sugar content of the resistant and susceptible plants decreased, and the soluble sugar content of the resistant varieties decreased by 71.698%.The content of free proline increased,the resistant varieties and susceptible cultivars increased by 400.000% and 100.000% respectively,and there were significant differences among varieties.The content of soluble protein increased,but there was no significant difference among varieties.The activities of POD,CAT,PPO and APX in resistant and susceptible mung bean cultivars increased after aphid infestation.The activities of POD and APX in resistant and susceptible mung bean cultivars increased by 66.886% and 137.417%,21.367% and 23.691%,respectively,but there was no significant difference among the varieties.There was a significant difference in CAT activity between resistant and susceptible mung bean cultivars and unaffected plants,with an increase rate of 236.515% and 124.426%.The PPO activity increased by 359.674% and 67.445% in resistant and susceptible mung bean cultivars,respectively.There were significant differences among cultivars.After the mung bean resistant and susceptible varieties are stressed by Aphis craccivora Koch,the changes of soluble sugar content,free proline content,CAT and PPO activity are related to the resistance of mung bean varieties.