Abstract: Stained with Aniline blue，combined with scanning electron microscopy，the grape downy mildew in susceptible variety‘Red Globe’and resistant variety‘Beimei’during the infection process were observed. To find out the similarities and differences of the infection process of Grape downy mildew in susceptible and disease resistant varieties. However，the number of sporangiophore，the branch of sporangiophore and number of stoma which were stretched out sporangiophore in Red Globe were higher than that in Beimei. The growth rate of mycelial of Beimei was slow，and the hypha in the late stage was less than that in the Red Globe. The gley period of Red Globe and Beimei was 4 d and 5 d. The time of appearance of long hypha，long and branch hypha and the loose mycelium were different in Red Globe and Beimei. In the late growth period，Beimei stays at the stage of loose mycelia and the mesophyll tissue of Red Globe filled with mycelium when it was inoculated at 96 h. The results of showed that there were significant differences in the frequencies of primary hypha and long primary hypha of haustorium formation in different varieties at the same time.

Key words: grape, Plasmopara viticola, infection process, gley period