The invention belongs to the technical field of tar and harmful component reduction of tobacco, and particularly relates to a CO2 flow extraction process for reducing tar and harmful components of tobacco. The process comprises the following steps of: performing liquid-state CO2 flow extraction; before extraction, performing microwave treatment on low-quality tobacco; and after extraction, performing solid-liquid separation to obtain the tobacco and drying to obtain a target product. Meanwhile, an extracted substance can be used as a raw material or a chemical material for manufacturing tobacco sheets by using a papermaking method after being treated. The process has the advantages of simplicity, safe used extraction agent, no need of refitting extraction equipment, low cost, environmental friendliness, economy and better tar and harmful component reduction effect of the treated tobacco.