A transient fault information based IED integrating protection, fault location, fault record, measurement and control functions for transmission line is proposed. IED hardware scheme adopts multiple CPU distributed structure, and includes mainly the following modules: process level communication module, protection module, fault location and record module, measurement and control module, station level communication module and a MMI module. Transient fault information utilization is illustrated in detail, which is mainly reflected in the protection module and the fault location and record module. Some key techniques are used to meet the smart substation development requirements. The multifunctional integrated IED can be applied in the existing smart substations, which can improve protection performance and fault location precision, and reduce equipment cost and operation and maintenance cost.