Abstract: Apple tree canker is one of main diseases of fruit tree in north china. Pathogens of canker （cytospora sp.）could make bark of apple tree decomposed by Pectolases. Many of epiphyte could excrete Pectolases. We mensurate the Pectolases produced by Pathogens of Apple tree canker and kuow that the pathogens could excrete Pectolases that activity very strong, it provided some foundation for control Apple tree canker.