Since the last decades， the transmission line protection relay coordination software has fast developed in terms of graphical interfaces and automation. However， the advancement in automation of relay coordination has not been able to help the protection engineers much from the complicated work for coordinated setting the relays. To reduce the protection engineers' workload， this paper investigates the automatic adjustment of relay coordination. A method for automatic adjustment of relay coordination of transmission line protection is proposed. The method is based on the reset relay sensitivity constraints， remote backup relay sensitivity constraints and remote backup relay sensitivity transfer constraints. The adjustment of relay settings is implemented by the relay coordination program instead of by the protection engineers. The case study shows that the proposed automatic adjustment method is efficient and practical.