After investigating and specimen collecting of Eucalyptus spp.die-back disease in Zhanjiang, Shaoguan and Huizhou in Guangdong province, pathogen isolation, pathogenicity test and pathogen identification were performed. The results showed that Fusicoccum aesculi Sacc., Glomerella cingulata (Stonem.) Spauld. & Schrenk. and Lasiodiplodia theobromae (Pat.) Griffon & Maubl. were responsible for the disease, joint infection by F. aesculi and G. cingulata was the main factor of its serious occurrence.