Abstract: The Path Coefficient method is used to study the hibernacula of apple-tree canker and the yield loss caused by it. The result shows that the pathogens of apple-tree canker hibernate in the last year's lesions which were not treated, its secondary hibernacula is those lesions that were treated last year but expanded again, the pathogens in twigs on the earth surface acted indirectly on re-infect after hibernation. The yield loss is caused by two factors: one is that the disease which occurs in the fruit and in the lateral branches, causes 71.96% loss, the disease occurring in the trunk aggravates the seriousness and affects the yield indirectly.