Abstract: The weed control efficacy and the safety to cotton of fluorochloridone in combination with pendimethalin or acetochlor were evaluated. Whole-plant dose-response experiments were conducted in greenhouse to evaluate the weed control spectrum of the single herbicide, the joint effect type and the selectivity index of the mixture. The results showed that fluorochloridone could effectively control most of the broadleaf weeds and part of grass weeds in the cotton fields, and the spectrum was complementary to that of pendimethalin or acetochlor. When fluorochloridone was mixed with pendimethalin or acetochlor, the joint effect type was either additive or synergistic, in the case of both Digitaria sanguinalis and Amaranthus retroflexus. When the mass ratio was 1:2, the herbicidal activity of the above two combinations were both improved, and the selectivity index between cotton and D. sanguinalis or A. retroflexus was in the range of 16.6-20.3, which suggested the safety of the above two combinations to cotton was improved compared to that of fluorochloridone and pendimethalin used alone.