In order to elucidate the mechanism of bacterial wilt resistance in grafted pepper (Capsicum annuum L.),Changes of root characteristics of grafted (‘Xinfeng 2’ scion grafted onto ‘Weishi’) and own-root plants (‘Xinfeng 2’,control) of pepper,quantity of microorganism and enzyme activities in rhizosphere soil were investigated by manual inoculation.The results showed that the root weight,total length,volume,surface area,root tips and forks,root activity,actinomyces quantity and ratio,and activities of polyphenol oxidase (PPO),peroxidase (POD) and dehydrogenase in grafted peppers increased significantly compared with those of control before inoculation.After inoculation,grafted plants showed a less damage in root than that of control plants.Grafted peppers had significant higher root weight,total length,volume,surface area,root tips and fork,root activity,quantity of microorganism and actinomyces ratio,and soil enzyme activities,in comparison with control.These data indicated that the observed increase in root system,root activity,quantity of microorganism,ratio of actinomyces,and enzyme activities in rhizosphere soil of grafted peppers are main reasons of enhancement of bacterial wilt resistance.