A waste heat recovery technics is used for CO conversion. The invention is characterized in that conversion gas recycles quantity of heat by a 1 conversion furnace, a medium-pressure waste pot, a 2 conversion furnace, a boiler water preheater, a 3 conversion furnace and a low-pressure waste pot, and then enters a low temperature formaldehyde washing reboiler and a desalting water preheater in turn after a 1 liquor condensate separator separates the liquor condensate to recycle reaction waste heat. The conversion gas enters the 2 liquor condensate separator and the conversion gas separated by the 2 liquor condensate separator is cooled 15 DEG C to not more than 40 DEG C by a conversion gas cooler, and then the conversion gas enters the 3 liquor condensate separator to be sent to the next working procedure. The generating low pressure steam is partly used for the steam of low pressure liquor condensate steam stripping. The invention has the advantages that a plurality of medium-pressuresteam and low-pressure steam are saved and the waste heat of the CO conversion is recycled thoroughly.