Because of its strong logicality and associability,the course "Organic Chemistry" is quite difficult for students majored in Environment Engineering.In addition,not all basic knowledge and theories required can be covered during limited class hours.To improve teaching quality and teaching effect,the Triple Representations strategy has been introduced in our class.It is expected that students can obtain knowledge from macro,micro and symbolic levels related closely to form a thinking model for all participants.In this investigation,the class teaching of "Free Radical Reactions" is selected as a example to present the practice of triple representations model.