In the Brown and Levinson's "face" theory,the core theory is a "threat face of the act",that is,discourse always contains varying degrees of each other or themselves in the face of the existence of many business English letters "face saving behavior of the damage factor in threat to the other side "because the parties in the transaction price of transaction,transportation,claims,Insurance,and inevitably on the other recommendations,opinions,requests or orders.In order to reduce damage to the other side of the case,you can use a virtual means,tactful tone,moderate expression of opinions,demands and suggestions.Thank you,