The invention relates to the technical field of chemical industry production, in particular to a formaldehyde waste heat recovery system. The formaldehyde waste heat recovery system comprises an air purifier which is connected with a roots machine through a pipeline, the roots machine and a high methanol tank are connected with an evaporator through the pipeline, the evaporator is connected with a filter through the pipeline, the filter is connected with a ternary filter through the pipeline, the ternary filter is connected with an oxygenizer through the pipeline, a heat exchanger is arranged in a reaction air outlet of the oxygenizer, the heat exchanger is connected with a first absorption tower through the pipeline, the first absorption tower is connected with a second absorption tower through the pipeline, the second absorption tower is connected with an exhaust gas boiler through the pipeline, the exhaust gas boiler is connected with a waste heat recoverer through the pipeline, and an absorbing liquid pipe of the first absorption tower is connected with the oxygenizer. Through improvement of a formaldehyde production unit, both steam consumption and energy consumption are reduced, and heat is recovered as much as possible.