The invention discloses a screening method for 110 types of medicines in feed, which specifically includes the following steps: preparation of standard work solution, pre-analysis treatment of sample to be assayed, creation of database and qualitative analysis. By utilizing the high-sensitivity MSMS (Tandem Mass Spectrometry) function of a liquid chromatography-tandem quadrupole time-of-flight mass spectrometer, the screening method can accurately determine parent ions and daughter ions in medicines and rapidly determine added medicine ingredients, moreover, an assay method for a variety of antibacterial medicines in feed is also established, and for a variety of added antibacterial medicines in the feed industry in China, the screening method has a highly efficient, accurate and precise assay measure, and is at the advanced level in china at present. The screening method established by the invention greatly solves the phenomenon of arbitrary addition in the feed industry, the more precise and accurate assay method is perfected for the inspection department, more time is saved, most of experimental consumables are saved, and the invention makes an immeasurable contribution to food safety and human healthy life.