Abstract: This paper reported that carboxylesterase activity of the resistant strains is notably higher than that of the susceptible strain, and observable relation with resistant factor. Factor of the resistance to omethoate, dicofol, amitraz and pyridaben on Tetranychus cinnabarinus were 152.83, 55.59, 62.61, and 15.67 folds, respectively. The relative specific activity of the carboxylesterase in the four strains were 3.52, 2.60, 3.24, and 1.73, respectively, and up while the factor is on the increase. Three rotational spraying strains, dicofol and amitraz, dicofol and omethoate, omethoate and amitraz in turn the resistant level to relative pesticides and relative specific activity were lower than that of spraying one pesticide to a batch. The relative specific activity of carboxylesterase were 2.06, 2.52, and 2.41, respectively. These results showed that increasing of the carboxylesterase activity is a one of biochemistry mechanisms of development of resistance to omethoate, dicofol, amitraz, pyridaben in T. cinnabarinus. In addition, the larger activity of the enzyme, the higher resistance folds on the spider mite.