The interference will greatly influence the performances of networks on its throughput, energy consumption, and lifetime in mobile ad hoc networks (MANET). On the basis of the existing interference models founded on the number and distribution position of the neighbor nodes, the traffic load of neighbors is further considered and an interference model based on traffic load is proposed. Based on the new interference model, a traffic load-based interference-aware routing (TIR) protocol is proposed, which chooses the routing path with the minimal interference between the source node and the destination node to reduce the possible interference generated when a packet is being forwarded. The results of the simulations show that the proposed interference model based on traffic load suits the characteristic of the MANET, and the TIR protocol obviously improves the network’s lifetime, communication delay and throughput.