Steelmaking process is a big consumer of energy. Converter steelmaking will produce a lot of coal gas which contains 60%-70% CO. It is very important to recycle the coal gas in steelmaking process. A method for purifying and recycling coal gas is wet dedusting. The limitation of this method will left high dust content in the coal gas after processing. In order to make use of this gas, two dust remover needed to be set to remove dust on the back side. Through online monitoring by gas analyzer after treatment, the flue gas can be recycled when it meets recycling requirements to reduce energy consumption and recycle development.