Abstract: The strain of Bacillus amyloliquefaciens 9601-Y2 (Y2)is helpful in diseases prevention in plants.The colonization of Y2 on maize leaves by spraying was investigated in order to clarify whether the strain could colonize or not.The results showed that Y2-pHAP Ⅱ suspensions were inoculated at 16:00 showed the strongest colonization in the greenhouse,while the number of viable strains,strains and spores of Y2-pHAP Ⅱ were dynamic consistent with the Y2-pHAP Ⅱ suspensions.The peaks of the number of viable cells,strains and spores of the suspensions were 5.13×106cfu/g,3.10×106cfu/g and 2.04×106 cfu/g at the 9th day after inoculation,respectively,while the fermentation liquid (FL) were 3.90×106cfu/g,2.65×106cfu/g and 1.25×106cfu/g.The 3 indices of Y2 suspensions and Y2 FL showed the similar curves and trends under the field conditions.At the 5th day,the number of viable cells and the strains reached 4.59×105cfu/g and 2.30×105cfu/g in Y2 suspension respectively,and 3.44×105cfu/g and 1.72×105cfu/g in Y2 FL.At the 12th day,the number of spores slightly increased to 1.17×105cfu/g and 4.03×104cfu/g.Under the greenhouse and field conditions,target strains were recovered in 40 days,while the colonization of Y2 suspension was improved by 25 % than Y2 FL.The results showed that a good colonization ability of the strains might be one of the effective disease prevention mechanisms.