Combining with the characteristics and current situation of college physics experiment，and based on PBL learning theory，it puts forward 2W2H teaching method，which is “why to do，what to learn，how to do，how about”，to help students construct learning main line and draw serial learning resources together with the four problems，and to promote students’active learning awareness and independent experimental ability．This method is applied to the teaching of digital oscilloscope experiment in college physics experiment course．Examples are shown to illustrate the idea and specific implementation scheme of this teaching method． The practical results prove the effectiveness of this method．