Abstract: Changes of trehalose and trehalase activity and expression levels of three heat shock protein genes in Bemisia tabaci were measured at 6, 12, 24, 48 and 72 h after parasitization by Encarsia sophia. Contents of trehalose peaked at 24 h and then decreased, while trehalase activity was low until 24 h after parasitization and then increased. Parasitization induced high expression of hsp90 gene but suppressed expression of hsp70 gene. Expression level of hsp20 gene increased in the early stage after parasitization and was then reduced. The three genes were differentially expressed starting at 12 h after parasitization. This study indicates the involvement of trehalose and heat shock protein in parasitoid-host immunity interaction.