Abstract: This study was designed to establish a high performance liquid chromatography (diode array detector, DAD)-tandem mass chromatography (HPLC-DAD-MS/MS) method for the simultaneously screening 12 kinds of cough-relieving chemical drugs illegally added in anti-cough and antiasthmatic traditional Chinese medicines. This method involved liquid chromatography-tandem mass spectrometry. The separation was conducted by Kromasil100-5C18 (250 mm × 4.6 mm, 5 μm) and the mobile phase was consisted of 0.3% ammonium formate (pH 2.97) and methanol. After separated by HPLC, the suspected components were analyzed by MS/MS and DAD and ultra scan was used to identify these illegally added drugs. A fast and sensitive HPLC-DAD-MS/MS method for the simultaneously screening for illegal chemical compositions was established. The LOD of these substances were below 50 ng. The method was sufficiently selective and sensitive to detect illegal chemical compositions in anti-cough and antiasthmatic traditional Chinese medicines.