Abstract: The effects of dextrin on the floatability of coal and quartz in flotation system and the inhibition mechanism were studied by flotation test, contact angle measurement and single mineral adsorption measurement. The results showed that when the amount of dextrin was 200g/t, the ash was 12.1%, and the clean coal ash was reduced by 1.53% compared with the unadded dextrin. The results of contact angle measurement showed that the contact angle of flotation clean coal increased after adding dextrin, and reached the maximum value of 96.26° when the amount of dextrin was 300g/t, which significantly improved the floatability of slime; The results of adsorption measurements show that the difference in adsorption of dextrin between quartz and coal surface is an important reason for the selective inhibition of dextrin. Dextrin has good selectivity when the initial mass concentration of dextrin is 24 mg/L. When the concentration of the dextrin agent is more than 24 mg/L, the selectivity of the dextrin is lowered, and the fine coal is prevented from floating.