Just like two sides of a coin,praise and criticism are the evaluations of the people's behaviors.Their purpose is actually consistent,which is to promote the students' growth.however,we tend to overestimate the side effects of the criticism but ignore the ones of praise.The side effects of praise are such as: on one hand,the students who get praise are led to their low drive,relying on praise,forming passive personality,and evaluating themselves incorrectly.On the other hand the students who have not obtained the praise feel hurt.Therefore,the teacher must grasp the skills of praise and take the right measures in the course of instruction.