To study the differences of three hybrids of Eucalyptus in volatile compounds and contents,we identified and analyzed the VOCs of Eucalyptus of different levels of resistance using GC-MS.201-2(E.grandis× E.camaldulensis)of high resistance contains 19 compounds,M1(E.urophylla × E.grandis)of high susceptibility 17 compounds,DH 32-29(E.urophylla × E.grandis)of susceptibility 24 compounds.The main compounds of the relative content of more than 0.5%numbered 9,8,8,respectively and accounted for 83.73%of the total volatile,12.31%and 83.73%,respectively.Three hybrids have 3 kinds of common compounds.The unique compounds of 201-2 numbered 13 kinds with a total content of 13.39%,whilst M 1 has 13 kinds accounting for 5.56%,and DH 32-29 has 16 kinds accounting for 80.98%.There are 4 kinds of ester accounting for 1.11%,3 kinds of acids accounting for 0.74%,and 2 kinds of ketone accounting for 0.59%,in the unique compounds of 201-2,DH 32-29 contains 1 kinds of ester and 1kinds of acids in the unique compounds.The results show that the VOCs of three hybrids are different.The high susceptible hybrids 201-2 inevitably own special compounds which could elicit an EAG reaction of L.invasa.The highly resistant and slightly susceptible hybrids may have compounds to defend them against L.invasa.Further more,the green leaf volatile,ester,acids and other VOCs may play important roles in the reaction mechanism of L.invasa to Eucalyptus.The study needs further research.