The asymmetric flow generated by the widely deployed address translation technology brings challenges to the design of load balancing system. To solve the problem of insufficient use of multi-core processors and network card hardware capabilities by software load balancers, an asymmetric flow load balancing method based on flow characteristics is proposed. Firstly, a data packet dispatching algorithm to dispatch packets into expected CPU core via hardware is proposed. Then, an elephant flow detection algorithm is constructed by analyzing of the temporal and spatial characteristics of packet sequences. Finally, based on detected results, a load balance offloading method is proposed. The experimental results show that, asymmetric flow load balancing method can correctly handle the asymmetric flow. Meanwhile, the average throughput rate increases by 14.5%.