Abstract: The fault detection mechanism based on network partition strategy is proposed in this paper. Firstly, the large-scale optical burst switching (OBS) network is partitioned into several subnet by network partition method, thus the fault monitoring can be achieved by the core nodes in each subnet respectively. Furthermore, with the probe module assigned in each subnet, the network fault can be detected by our cycle cover method. Numerical results show that the fault localization ratio can be improved significantly by our fault detection mechanism for the case of average node degree higher than 3.0; at the same time, the monitor cost can be reduced effectively.