Essential oils (EO) in peels and leaves of Citrus species including Citrus reticulata (Quyt duong and Quyt hong) and Citrus grandis (L.) Osbeck (Buoi da xanh and Buoi nam roi) were extracted by steam distillation. The extraction yield of leaf’s EO (0.08-0.38%) was lower than that of peel’s EO (1.78 -5.67%). Results of chemical analysis by mass spectrometry (GC/MS) showed that the main composition of peel EO contained limonene (86.63% -90.62%) and others as α- pinene (2.12% - 3.53%), β-myrcene (2.76% - 4.31%), β-pinene, β –linalool, β-phellandrene and octanal while leaf EO was  diverse in components including monoterpene hydrocarbon, sesquiterpene hydrocarbon and oxygenated- monoterpene and sesquiterpene such as limonene (3.76% - 8.54%), β-ocimene (5.0% - 14.11%), γ-terpinene (2.08% - 12.66%), β-pinene (5.34 - 28.01%), caryophyllene (2,24 - 6,68%), β-linalool, β-thujene, 1-terpinen-4-ol, nerol, neral... The results of antioxidant activity (using DPPH method) indicated that the leaf EO gave stronger activity than peel EO, but both were weaker activity than vitamin C. Our findings from Citrus EO possesed antifungal activity on disease fungi of plant (F. fungus, Colletotrichum sp.) and of aquaculture (Achlya sp.), but they were more significant on disease fungi of aquacultural animals (Achlya sp.)