Political euphemism is a tool for political leaders to control information transmission. Based on some examples, this paper begins with a summary of three features which distinguish political euphemism from others. Then, it discusses its two social functions based on Austin's Speech Act Theory: 1) as political leaders' tool, political euphemism plays the role of hiding the truth and legalizing wrong behaviors; 2) it influences people's sense of right and wrong as well as their understanding of the objective world, hence succeeding in persuading them. Such a linguistic phenomenon provides another proof that language is not only a reflection of the objective world but a process of social construction.