A novel fiber-optic chaos synchronization system allowing bidirectional long-distance chaos communication is proposed. For this system, chaos synchronization between two response lasers (RLs) is achieved via an identical driven chaotic signal injection from a remote driving laser (DL) over a long-distance fiber. The simulated results show that under suitable operation conditions, high-quality chaos synchronization between the two RLs can be obtained while the synchronization quality between any one of RLs and the DL is bad, which is useful for improving the system security. Using the two synchronized chaos output signals from RLs as two chaotic carriers and adopting a novel message encryption and decryption method, the communication performances, the impact of long-distance fiber channel and the security of this system, have been analyzed. After adopting an optimized system configuration, two 10 Gb/s messages propagating along opposite direction can be effectively decrypted over 100 km fiber channel.