Abstract: By infection with Fusarium oxysporum in greenhouse,bacterial physiological flora of cucumber rhizosphere was changed and enzymatic activities decreased.The population of nitrobacteria and nitrite bacteria decreased in the early and peak phases of infection,thereafter which enhanced growing of aerobic azotobacter and denitrifier.The population of ammonifying bacteria and cellulose-decomposition bacteria consistently decreased during infection period.The population of rhizosphere thiobacillus dropped dramatically concomitant of increase in anti-sulfuration bacteria.The impact of nitrobacteria in cucumbers was significantly different between susceptible and resistant varieties,which may play an important role in physiologic accommodations against of cucumber Fusarium wilt.After Fusarium oxysporum infection,the activities of rhizosphere enzymes were declined significantly in catelase,urease,cellulase and alkaline-phosphatase.In early infection,the decline of activities was observed for catelase and cellulase more remarkable in susceptible varieties than in resistant varieties.However,the extent of decline in late of infection was found for urease and phosphatase but more remarkable in resistant varieties than that in susceptible.The impact of catelase in resistance to the disease was different significantly between susceptible and resistant varieties,which can be used as reference in resistant breeding.