The differences of the total phenolic content in leaves and percentage of cotton plants infested with cotton spider mites between in transgenic Bt (Ezamian No. 24F1) and in non-transgenic Bt cotton (Ek 9 parental line of Ezamian No. 24F1) plots with and without spraying acaricides were systematically investigated in Tai Lake farm, Hubei Province, China, over the period 26 May and 11 September 2011. In acaricide treated plots, transgenic Bt cotton does not result in a change of the abundance of cotton spider mites compared to that in non-transgenic Bt cotton, however, without acaricide treated plots, transgenic Bt cotton significantly increases the abundance of cotton spider mites compared to those of non-transgenic Bt cotton. The number of eggs, larva-nymph-adults, egg-larvanymph- adults and the plant damage index are independent of the total phenolic content in leaves. The results are also discussed in relation to integrated pest management. It was very necessary for nontarget cotton spider mites of transgenic Bt cotton fields to control in wetland agricultural area.