The following conclusions become evident. On the theoretical aspect: first, the main concepts of critical thinking include critical thinking ability, critical thinking disposition and the knowledge for critical thinking; second, the steps of the model for teaching critical thinking are guiding activities, displaying theme, comparing concepts, group discussion, sharing and clarifying, and finally, judgment and decision-making. On the experimental aspect: it was found that (a) Teaching critical thinking has significantly positive effects both on critical thinking ability and on critical thinking disposition. (b) Teaching critical thinking helps students have good performance in debates. (c) The students of experimental group make great progress on achieving confidence in reason and pluralistic thinking. (d) The students of experimental group give a vary positive evaluation on teaching critical thinking.