For reasons of scalability and security, the hierarchical routing architecture with topology aggregation is introduced to Automatically Switched Optical Network (ASON). By aggregating the topology and routing information, operators can shield the internal details of their optical networks and configure their networks arbitrarily. This work addresses the problem of topology aggregation in hierarchical ASON network. A novel aggregation scheme based on minimum spanning ring (MSR) is suggested. We compare the proposed scheme, by simulation, with several different schemes studied before in terms of the network throughput, traffic distribution and network stability. The simulation results show that the aggregation scheme based on MSR can yield very good overall network performance. The outstanding performance together with simplicity of calculating for a minimum spanning ring makes it a very attractive candidate for use in practice.