Abstract: The transmission of coordination messages caused by the decomposition-coordination process in large-scale networks was investigated．Two principles‚one is that the shortest total distance from the central agent to other agents is the minimum one of the distances of all possible schemes‚the other is that the time cost of the message transmission from the central agent to other agents following the shortest distance is also the minimum one‚which are used to select the central agent were proposed according to two different optimized objectives‚such as the minimum communication cost and the minimum waiting time of each agent．The corresponding routing algorithms for coordination messages were also provided．An example was finally given by which the process of selecting the optimal central agent via the two al -gorithms was illuminated． 

Key words: network, routing, coordination message, optimization, central agent