Abstract: In order to explore the action mechanism of the resistance to cucumber grey mould induced by biocontrol bacteria ZJH-10, the physiological and biochemical methods were employed to study the changes in contents of malonaldehyde(MDA), protein, soluble sugar, Vc, chlorophyll and carotenoid in cucumber roots and leaves pretreated with biocontrol bacteria ZJH-10 and Botrytis cinerea. The results showed that the contents of MDA in the roots and leaves treated by ZJH-10 are lower than those of other treatments to some extent and reached their minimum on 5th.The contents of protein, soluble sugar and Vc in roots treated by ZJH-10 obviously increased higher than those of other treatments and reached their maximum on 5th, 3rd and 5th in roots, and the contents of these substances in leaves were accorded with those of substances in roots. Moreover, the contents of chlorophyll and carotenoid in leaves treated by ZJH-10 obviously increased higher than those of other treatments and reached their maximum on 3rd. Accordingly, biocontrol bacteria ZJH-10 may enhance the resistances to gray mould by changing the content of these substances.