Letter of Credit (L/C) is a primary way of payment in an international steel trade. However, due to the risks of documentary fraud, it is a great challenge to the confidence of L/C service in the complex trade environment. Firstly, this paper summarizes the methods and specific characteristics of L/C service in the steel trade, and also realizes the risks of confidence in the process of international transaction. Then, based on underlying technology and characteristics of blockchain technology, a new solution will be conducted related to L/C service to solve the weakness of L/C, including the documentary fraud, long payment cycle, repeated operations and high additional costs.