Due to the problems in the theoretical teaching for engineering majors in large-size class,a teaching method of PAD(Presentation-Assimilation-Discussion) is introduced.The method can effectively organize classroom teaching and enhance the students' learning enthusiasm.The idea of PAD Class is analyzed in term of viewpoint of knowledge presentation,knowledge assimilation and team discussion.The implementation program of PAD class is elaborately designed by this idea.Several modern teaching tools are developed and used in PAD class.Classroom teaching practice data shows that the class teaching quality can be improved via PAD which is also a good reference method for promoting the teaching reform.