Abstract: Experimental teaching based on large scale instruments is always difficult because of the insufficiency of instruments and complicated procedures. In such classes, the students usually show little enthusiasm for the relatively less opportunities to perform the instrument. In consideration of these problems, a new teaching mode of cooperative learning is used in the experimental classes of measuring the particle size of water mist with shadowgraphy. Hierarchical experiments with basic and exploring ones are designed to create an open and cooperative atmosphere. Moreover, the scores in the course are evaluated by teachers and students through peer review. The reformations are expected to motivate the interest of students, train their experimental skills and further develop their innovative ability and cooperative spirit.