The effects of various kinds of inorganic acids on the content,cation exchange capacity and optics nature of humic acid in brown coal were studied. The content and the optics nature were not affected by phosphoric acid and hydrochloric acid treatment,but can be increased the exchange capacity to some extent. The content of humic acid can be increased by 25 per by suitable for intensity nitric acid, The cation exchange capacity can be greatly in- creased and the optics characteristic was greatly changed. The best condition would be different to different brown coal.