Abstract  [Aim]  To clarify the population structure and host preferences of the spider mites Tetranychus dunchuangensis Wang and T. truncatus Ehara, important pests that damage a variety of crops and vegetables. [Methods]  The population dynamics of T. dunchuangensis and T. truncatus on Gossypium hirsutum L., Zea mays L., Citrullus lanatus (Thunb.) Matsum. et Nakai, Arachis hypogaea L. and Beta vulgaris L. were investigated in Korla. The leaf disc test was used to study the preferences of these spider mites for different host plants in a laboratory. [Results]  T. dunchuangensis began to occur on host plants in mid to late June, and T. truncatus in mid to late July. The number of both spider mites peaked from late July to early August, then gradually decreased in late August. The two spider mites first damaged C. lanatus, but the largest populations occurred on A. hypogaea. Numbers of both species were lowest in Z. mays and G. hirsutum, respectively. The average number of T. dunchuangensis was significantly higher than that of T. truncatus on G. hirsutum and C. lanatus (P<0.01), but there was no significant difference in the abundance of these species on A. hypogaea, B. vulgaris and Z. mays (P>0.05). C. lanatus was most preferred by T. dunchuangensis, whereas T. truncatus preferred G. hirsutum. [Conclusion] T. dunchuangensis is the dominant spider mite in the local area. It occurs early and has can attain a relatively large population size. T. truncatus occurs later and has a smaller population than T. dunchuangensis. It is important to avoid planting crops preferred by spider mites near main crops, or to use preferred host plants as trap strips for concentrated pesticide application. For example, where T. dunchuangensis is the dominant species, avoid planting B. vulgaris next to G. hirsutum crops and C. lanatus next to A. hypogaea. Where T. truncatus is the dominant species, avoid planting A. hypogaea or B. vulgaris next to C. lanatus. Where crops have already been planted near preferred host plants, it is important to intensify monitoring and implement control measures at the right time to mitigate the impact of spider mites on crop yields.