A method of forming a frame in a Mobile Multi-hop Relay (MMR) system, and a system for implementing the method are provided. In a multi-hop relay system, when a relay station of a specific layer receives data, the relay station receives data from both a higher layer and a lower layer. When the relay station transmits data, the relay station transmits data to both the higher layer and the lower layer. By doing so, data reception and data transmission are exclusively performed without interfering with each other, and the method and the system are easily applied to the multi-hop MMR system.