Proceeding from the basic principles of maritime and civil laws,this article, by refering to judicial practice,analyzes the legal characters of the letter of indemnity, its validity, invalidity and scope in gaining clean bill of lading. Meanwhile the author presents his point of view that the letter of indemnity should be annexed with extra conditions. The article also discusses some methods in distinquishing between letters of indemnity in good faith and malicious ones. Finally,it reaches the conclusion that the validity of letter of indemnity only involves the carrier and consignee. The auther suggests that China should stipulate clearly the validity of letter of indemnity inmaritime legislation.