Abstract: Whole-plant dose response experiments were conducted in greenhouse to evaluate the control efficacy to Eleusine indica, Digitaria sanguinalis, Portulaca oleracea, Amaranthus retroflexus and Cyperus rotundus, the safety on different cotton varieties, and the selectivity index between cottons and weeds of the combinations of trifloxysulfuron and quizalofop-p-ethyl. The results showed that combinations of the two herbicides had synergistic or additive activity to C.rotundus and P.oleracea, and additive activity to A.retroflexus, E.indica and D.sanguinalis. When the mass ratio of trifloxysulfuron and quizalofop-p-ethyl was 1:3, 1:4, the mixture was safe to all cotton varieties at application rate of 80 g/hm2; however, when the application rate increased to 160 g/hm2, the safety of the mixture to different cotton varieties varied greatly, and the safety to Lumianyan 36 was higher than that to Shannongmian 8. The selectivity index between cottons and weeds of the combinations was significantly higher than that of trifloxysulfuron alone, which suggested combination of trifloxysulfuron and quizalofop-p-ethyl improved the safety on cotton.