The present invention discloses a carbon monoxide conversion process for preparing synthetic ammonia by using coal or residuum as raw material. Said process does not adopt saturation tower, but uses cleaning agent to implement the purification treatment of semi-water gas to remove the impurities of oxygen, etc. harmful to low-temp. conversion catalyst, and the Co-Mo series low-temp. conversion catalyst is filled in the convertor. By reducing conversion temp, the ton ammonia steam consumption of said conversion process having no saturation tower only is about 300 Kg.