Abstract: In three-dimensional Network-on-Chip, the faults occurring in the horizontal and vertical links will decrease the performance of the entire network seriously.We propose a novel low overhead and high efficient fault-tolerant method—apriority based deflection routing method.The new method dynamically change the priority of output port to ensure that data packet always chooses an optimal route based on the relative position between destination node and source node.With combining the two-level switch crossbar router architecture, inter-level and intra-level data packets transmit efficiency could be improved.A series of experiments with Booksim 2.0and Orion 2.0 were conducted, experimental results demonstrated that our algorithm outperforms others by up to 20%in terms of average packet delay of network.When network size increases, the area overhead does not increase apparently, thus the overall performance of network is improved significantly.