A hierarchical region defensive system (RDS) based on optical fiber communications is proposed in this paper. This system comprises three layers. The bottom layer is the local measuring unit (LMU), which is equipped in those corresponding substations within this region. The intermediate layer is region decision layer comprising region decision units (RDUs). Every RDS has one RDU, which is connected with all LMUs within this region by means of optic fibers. The system monitor center on the top layer is mainly responsible for harmonizing and monitoring every RDU, recording the fault occurrences and adjusting the protection settings. This system offers safeguard to key region where energy converges inside the power network utilizing multipoint information, which cooperates with conventional main and backup protections. The hierarchical structure and operating principle has been detailed elaborated, especially the working process of measuring elements and decision-making elements. Various complicated fault scenarios within and out of the protected region are simulated using Electromagnetic Transients Program software to validate the proposed defensive system, and the results approve the correction of this system. Finally, the implementation of prototype of region protection system and the scenarios of dynamic simulation tests are provided.