The active metabolites of Aspergillus fumigatus isolated from Neriumindicum Mill. Cv Paihua were studied. All 6 isolated and identified compounds were as follows: alternariol, 4-acetylaminobutyric acid, monomethylsulochrin, succinic acid, cyclo-（ala-val）, and homogentisic acid. Alternariol had an inhibitory rate of 91.8%, 89.1%and 90.6% against Alternaria brassicae, Cytospora sp. and Colletotrichum gloeosporioides respectively, higher than that of the positive control. The inhibition rate against Botrytis cirerea and Fusarium oxysporum. sp. cucumebrium Owen was 86.6% and 84.3%, respectively, the same as the positive control. Alternariol had a strong antibacterial effect on all 4 bacteria tested. This study provides a theoretical basis for the development of new microbiological fungicides and plant diseases controlling.