Abstract: In the synthetic ammonia plant with the annual production of 3,000 tons of synthetic ammonia,the method of tannin extract in the industrial production experiment for the desulfurization of H₂S in the semi water gas was carried out.The result was fairly good. The principle of desulfurization in this method was in general similar to that of the improved method of ADA.The tannin extract possessed more hydroxyl and carboxyl groups.In alkaline medium it possessed rather strong oxygen-absorbing power.It was a good oxygen carrier in oxidation process. Under the following conditions:pH of the desulfurization liquid was 8.5—9.0;the total alkalinity was 0.7—0.8 N;sodium metavanadate was 2—2.5 g/liter;tannin was 0.6—1.0g/liter;regeneration temperature was 35—45℃;the amount of regenerated air was 450—550m³/hour,it was possible to reduce the amount of H₂S in semi water gas to less than 0.1g/m³.The efficieney of desulfurization reached 99%.The recovery of sulphur was 85—90%.