Abstract: Biochmicah humic acid (BHA) was applied to prevent and control apple tree disease caused by Physalospora piricola in 1996. The results proved that the active substances in BHA provoked apple trees and improved their nutrition regulation and adaptability to environment along with the change of physiological and biochemical index. Activity of super oxide dismutase (SOD) and the process of metabolism in apple trees were strengthened.Thus the content of phenolic acids,a kind of inherent anti biotic substances in apple trees were significantly increased,and P.piricola disease rate was reduced,photosynthesis was enhanced, synthesis was promoted. And nutrition in apple trees was accumulated. The opening degree of stomata was changed also. It′s concluded that weak apple trees were rejuvenated and the pesticide′s effect could be brought into full play. The rate of the disease could be reduced to less than 40%.