Large data RDMA (Remote Data Memory Access) transport is the most commonly used parallel communication mode for parallel computers, which has great impact on the whole system performance. As the system size increases, the fault-tolerate architecture design faces new challenges. The interconnection network usually uses the adaptive routing mode and becomes more unreliable. This paper proposed a fast RDMA offload method for unreliable interconnection networks, which can be efficiently implemented on the NIC hardware and provides reliable RDMA communication for upper driver and programs. Compared with the traditional approaches, the hardware overhead is greatly reduced. Another benefit is that it can partially retransmit the fault data, which greatly reduces the whole RDMA delay. Simulation results show that the RDMA delay is greatly reduced, compared with the traditional methods.