Efficient transmission of message data is a research focus of hybrid networks. Publish/subscribe is the messaging pattern to realize the decoupling between publisher of messages and subscriber of messages, which is suitable for message data transmission between hybrid networks. By applying the publish/subscribe model to message data exchange, the format of message data is standardized, flexible management of various communication devices, and dynamic data routing based on message content. Along with publish/subscribe, a dynamic load balancing algorithm based on the round-robin scheduling is proposed to improve performance of low-rate networks. Simulation experiments are carried out, and the experimental results show that publish/subscribe model achieves reliable message data transmission between hybrid networks, and it performs better with load balancing.