The occurrence of Bemisia tabaci poses an increasingly serious threat to cotton and vegetable crops in Xinjiang, China. Currently, neonicotinoid insecticides are commonly used to control the insect, to which resistance is inevitable due to intensive use. However, the resistance status and mechanism of B. tabaci to neonicotinoid insecticides in Xinjiang are poorly understood. Cytochrome P450 monooxygenases represent a key detoxification mechanism in the neonicotinoid resistance of B. tabaci. In this study, the resistance level to imidacloprid and thiamethoxam was investigated using the leaf dipping method in five field populations of B. tabaci from Turpan (TP, two sampling sites), Shache (SC), Hotan (HT) and Yining (YN) in northern and southern Xinjiang. The expression changes of eighteen cytochrome P450 genes from the select B. tabaci populations were determined by real-time fluorescence quantitative PCR (qPCR). The bioassay revealed that the five populations tested had developed moderate to high levels of resistance to imidacloprid (12.26-46.07fold), while the populations remained sensitive to thiamethoxam except for HT, which had a low level of resistance. The qPCR results showed that the expression levels of five P450 genes, CYP4G68, CYP6CM1, CYP303A1-like, CYP6DZ7 and CYP6DZ4, were significantly higher in some resistant field populations than in the susceptible strain. Resistance to imidacloprid in field populations of B. tabaci might be associated with the increased expression of these five cytochrome P450 genes. The results are useful for further understanding the mechanism of neonicotinoid resistance and will contribute to the management of insecticide-resistant B. tabaci in Xinjiang.