Abstract: This paper comes up with a kind of low delay NoC fault-tolerant mechanism which is based on router bypass channel. Firstly, the bypass channel and error detection device are added into this mechanism to achieve fault-tolerance in the router. Secondly, the multilevel congestion control concept is introduced to reduce the NoC delay in fault-tolerant routing algorithm. The simulation was conducted by using the NIRGAM platform. The experimental results show that, comparing the fault-tolerant routing algorithm proposed in this paper with the ASL-XY algorithm and low delay and reliable transmission algorithm, the network average delay is reduced significantly, and with the packet injection rate increasing, the network average delay rate growth in the proposed algorithm is obviously lower than the one in the other two algorithms. It's effectively proved that its excellent performance of NOC fault tolerance mechanism is designed in this paper.