Abstract: After pear(Pyrus bretschneideri Rehd.cv.Yali)leaves infected with Venturia nashicola,the permeability of cell membrane increased,photosynthetic rate dropped, the totalphenols content and the activity of polyphenol oxidase and peroxidase isoenzymerose.There was an additional band o f peroxidase isoenzyme sho wing up in the fastband area.