In business contacts, the business correspondence is not only the medium for communicate, but also a means of establishing friendship and attracting customers. The features and functionality of business correspondence decide that the letter must pay attention to the politeness principle. The success of writing it has an extremely important impact on the business of a company. Thus, in day-to-day business activities, we should noted the application of the politeness principle in the Business English writing in order to promote better co-operation and communication in the future business..