Abstract: Clenbuterol, also known as lean meatines, is a β-stimulant hormone. Lean meatiness will promote animal growth and increase lean meat rate, which has been widely used as feed additive. However, the overuse of lean meatiness often forms residues in animals, and human consumption of lean meat essence residues can lead to acute poisoning, organ damage and even life-threatening. Although clenbuterol has long been banned in China, it is still used secretly by many merchants for profit. The production, sale and use of "lean meat essence" not only endanger the health of the people, but also endanger the sustainable and healthy development of aquaculture and social stability. Therefore, the development of rapid and effective detection methods to regulate the market can effectively prevent such things. A method of thermal analysis of low temperature plasma ion source combined with time of flight mass spectrometry (TD-LTP-MS) was developed for rapid screening of six lean meatines (simaterol, terbutaline, sebuterol, clenbuterol, malbuterol, and machaterol) in feed. Helium flow rate and thermal desorption temperature are important factors to determine the performance of low temperature plasma ion source. Increasing the helium flow rate can increase the active substances such as Hem and N₂⁺, thus improving the ionization effect. The lean meatines veterinary medicine generally has the higher boiling point, so higher thermal desorption temperature is advantageous to desorb them from the solvent. In this study, the low temperature plasma ion source conditions were optimized in the range of helium flow rate of 0.3-1.9 L/min and thermal desorption temperature of 160-260 ℃. Finally, the helium flow rate of 1.0 L/min and thermal desorption temperature of 210 ℃ were the optimum condition for the ionization of six kinds lean meatines. The sample was extracted by 10 mL 0.1% acetonitrile oscillation for 5 min and then centrifuged at 2 500 r/min for 2 min. The supernatant was added 250 mg PSA and 50 mg C18 to purify the sample. The final sample was analyzed by TD-LTP-MS method in positive ion mode. Results showed that there were good linear relationships for the 6 analytes in the range of 5-500 μg/kg with the correlation coefficients greater than 0.992. The detection limits were lower than 3.1 μg/kg and the recovery rate was 71.4%-119.2%. The method is simple and fast, without tedious pretreatment, and is suitable for high-throughput screening of lean meatine in feed.