Abstract: The experiment was carried out in the period from 1989 to 1992. The author took the winter buds, Young leaves,tender leaves,tender leaves and overwintering fallen leaves of Oinkgo as experimental materials. The results demonstrated that all the three pathogens (Alternaria alternata, Col-letotrichum gloeosporioides, Pestalotia ginkgo) of ginkgo leaf blight overwintered on winter buds and fallen leaves in the form of mycelium. During the spring (after the germination of buds), the main pathogen-A. alternata of ginkgo leaf blight could be transferred to a part of tender leaves and continued its incubating infection, But there was a marked drop in quantity. During the months of March to June, clumped conidiophores were formed by A. alternata on the overwintering fallen leaves, and new conidiodpores constantly emerged. The conidiospores formed on the fallen leaves last year still retained the germination capacity to a certain degree. So far as the carriers were concerned, the winter buds could not be compared with fallen leavs in the sense of infectious source.