Gas pipeline requires to be inspected regularly for leakages caused by natural disaster. Robots are widely used for pipeline inspection since they are more convenient than manual inspection. Several problems, however, exist due to the restriction by complex pipe networks. The most significant one is limited inspection range caused by restriction of cable length or wireless signal attenuation. In this paper, we proposed a concept of wireless relay communication to assist robot to extend the inspection range, and we newly developed a tracked robot chain system. In this system, each robot serves as a relay communication node. Leakage information of pipes are transmitted via these relay nodes. To ensure the stability of relay communication between adjacent robots, we adopted RSSI (received signal strength indication)-based evaluation method for cooperative and coordinated movement of robot chain system. Moreover, wireless application layer communication protocol (WALCP) was used to increase the stable performance of wireless relay communication. Each robot can self-navigate based on distance measurement module, which enables robots to pass through an elbow junction. Multiple experiments to evaluate relay transmission efficiency, RSSI-based cooperative movement, and comprehensive performance were conducted. Results revealed that our proposed system could realize relatively accurate relay transmission and RSSI-based coordinated movement.