Abstract: A new method of High-Performance Liquid Chromatography (HPLC) was reported. As the absorbent, saturated solution of 2,4-dinitrophenylhydrazine with acidity, reacts with aldehydes and ketones in ambient and polluted air, this reaction generates 2,4-dinitrophenylhydrazones, which can be determined by HPLC. In this method, the recovery ratio of pretreatment is 90%～100%, the lowest detection limits are 1～5 ng, and the linear operating range is 5～300 ng. This method can determine 10 kinds of aldehydes and ketones in ambient air and workshop air.