The opportunity to isolate a considerable number of humic acids from the brown coal thermooxidative treatment products in the presence of small portions of oxygen and water has been shown. Variations in the functional content, thermal stability and biological activity of the prepared humic acids depending on the conditions of coal thermal processing have been revealed. It has been found that under the conditions of mild thermooxidative destruction a semicoke may yield up to 37.4% of the so-called ＇high-temperature＇ humates and residual coal whose methylene-blue activity is 207.5 mg/g which is equal to that of the good activated carbon.