Optical network on chip (ONoC) is an emerging paradigm for multi-core processor system for providing high bandwidth and low power consumption. The scalability of the multi-core processor system is limited by process yield and power density of the single chip. Multi-chip ONoC, which aggregate several smaller chips together, is proposed to overcome this problem. Nesting Ring Optical Network on Chip (NRO) is a multi-chip architecture, which has good performance in terms of throughput and delay. When the NRO scales to a large size ONoC architecture, it may suffer from severe congestion. We propose a novel resource reservation scheme for NRO to alleviate this problem. The resource reservation includes resource planning strategy and a Resource Allocation strategy. With our observation, lots of contentions occur in intersection nodes due to the lack of resource, because intersection nodes have heavier traffic than normal nodes. The proposed resource planning strategy can offer more optical resource for intersection nodes specifically, and keep the original number of wavelengths in the normal nodes, which maintains good power efficiency of NRO. Additionally, unreasonable resource allocation method will lead to contentions. We employ backward resource reservation method in NRO architecture to avoid contentions in intermediate nodes of the path. The simulation results show that the proposed resource reservation scheme can reduce 85% blocking rate and 12% ETE delay compared with convention scheme at an injection rate of 0.4.