Abstract: This is an essay in the field of mineral processing engineering. Humic acid is an important part of Zhaotong lignite. In order to extract humic acid efficiently, the optimum flotation conditions of Zhaotong lignite were explored by using the process of direct flotation and reverse flotation. Orthogonal experiments were designed by using the method of oxygen decomposition and alkali solution-acid separation to extract humic acid from flotation cleaned coal, and the optimal conditions of humic acid extraction were explored. The results show that the positive flotation collector consumption is large, and under the condition of surface modification of Span 80, the flotation cleaned coal yield is the highest of 26.64% and ash content is the lowest of 20.08%; the optimum conditions of reverse flotation are laurylamine 5 kg/t, dextrin 3 kg/t and foaming agent 260 g/t, and the optimum flotation indexes are as follows: flotation cleaned coal yield 84.35% and ash 20.52%, flotation tailcoal yield 15.65% and ash 36.75%, and flotation perfection index 12.08; the optimum extraction conditions of oxygen decomposition are as follows: H₂O₂ concentration 0.7 mol/L, H₂O₂ activation time 35 min, NaOH concentration 0.3 mol/L, NaOH soaking time 30 min, and the extraction rate of humic acid 37.14%; the optimal extraction conditions of alkali-soluble acid chromatography are as follows: concentration of hydrochloric acid 10%, activation time of hydrochloric acid 30 min, NaOH concentration 0.7 moL/L, NaOH soaking time 30 min, and the extraction yield 43.80%. Reverse flotation can obtain higher yield of high ash flotation clean coal than normal flotation, and the extraction rate is higher when the humic acid of Zhaotong lignite is extracted by alkali solution-acid separation method.