Clenbuterol was used as decongestant and bronchodilator to treat respiratory diseases in human and animal.It belongs to the class of beta-agonist compounds known for growth promoting properties.USDA, US FDA and EU have banned the use of clenbuterol for human and livestock due to its potential health risks to human, such as disruption of lung and heart functions.But it has been illegally used to generate low fat meat in food-producing animals, and to stimulate muscle growth by some sport players.It is thus necessary to establish screening test method with high sensitivity to monitor clenbuterol residue in urine.