The responses of the enzyme activity of carboxylesterase (CarE), glutathione\|s\|transferase (GST) and multifunction oxidase (MFO) in Bemisia tabaci to host shift were investigated in this study. Host shifts include from tomato plants (a high preference crop) to GK 22 cotton, Simian 3 cotton and capsicum plants (3 relatively low preference crops) and from capsicum plants (a low preference crop) to GK22 cotton, Simian 3 cotton and tomato plants (3 relatively high preference crops), and also include that the F4 generation of B. tabaci on the new hosts was transferred back to the original hosts. Our results suggested that the enzyme activity of CarE, GST and MFO in B. tabaci was related to the host preference. The activity of the three detoxification enzymes in B. tabaci on the high preference host plants was relatively low. After being transferred from the high preference hosts to the low preference hosts, the enzyme activity of CarE, GST and MFO in B. tabaci was significantly increased. After being transferred from the low preference hosts to the high preference hosts, the enzyme activity of CarE, GST and MFO in B. tabaci was significantly reduced. During host shift, the activity of CarE and GST in B. tabaci was usually stabilized in the F2 generation, while the activity of MFO could be rapidly stabilized in the F1 generation. During the shift from the transitional hosts to the original host plants, similar trends were observed in the activity of CarE, GST and MFO. In addition, during the host shift, the activity of MFO in B. tabaci responded and was stabilized rapidly, while the changes of CarE and GST corresponded to the adaptability of host change.