Multi-granularity switching in optical layer has gain significant importance due to the reduction of size and cost of the optical
cross-connect. In this paper, we propose a novel structure of MG-OXC, named two-layer MG-OXC, and also give a new graph model for describing the function of the all kinds of MG-OXC. The network states can be represented completely through our auxiliary graph. In such an auxiliary graph, the optical tunnel allocation in
multi-granularity switching network is reduced to the min-cost path find problem, and different traffic grooming policies can be archived simultaneously. We compare the performance of the two-layer MG-OXC to the normal three-layer MG-OXC and single-layer MG-OXC by the algorithm we proposed through simulation, and conclude that the novel MG-OXC can get very close performance to threelayer MG-OXC but smaller size of switching matrix. The simulation also proved the algorithms we proposed performs better than traditional RWA algorithms dealing the routing and wavelength sub problems separately.