Abstract: OBJECTIVE To determine the scavenging ability on ROS free radical of polysaccharides in Tussilago farfara in vitro by flow injection chemiluminescence. METHODS The determination was based on the inhibition effect of Tussilago farfara polysaccharides extraction in three chemiluminescence system, and vitamin C was used as positive control. RESULTS It was showed that Tussilago farfara original liquid could inhibit and clear the ROS such as O₂^-·, ·OH and H₂O₂ effectively, and the efficiency was related to the concentration of polysaccharides in Tussilago farfara in the concentration range from 0.25 to 4.4 mg·L^-1. The scavenging abilities of polysaccharides in Tussilago farfara on ROS was ·OH>H₂O₂>O₂^-·. CONCLUSION The polysaccharides of Tussilago farfara have an antioxidation effect within a range of certain concentration in vitro.