Abstract: The gray-mold disease of peony and tree peony has been found in Nanjing, Hangzhou, and shanghai. This pathogenic fungus always causes leaf-spots of both hosts, especially after their flowers fade. After artificial inoculation, the fungus will attack hotpeppers, cucumbers, eggplants (aubergines), tomatoes, and grapes. Its conidia are colourless to pale brown, elliptic or ovoid, 8.0-15.0×7.0-10.0μm. According to its morphological characteristics and hosts, the causal pathogen of this gray-mold disease is identified as Botrylis cinerea Pers. ex Fr. The optimum temperatures for its mycelial growth are 20-40°C, and the optimum pH values, 4-8. The fungus is easy to sporulate in 6°Be-malt-extract agar medium and the spore easy of conidial germination in 8°Be malt extract.