In the past ten years, considerable increases in traffic volume and vehicle loads have caused obviously fatigue damage in existing highway reinforced concrete bridges in China. Some highway reinforced concrete bridges were damaged seriously, leading to the whole bridge collapse sometimes because of overloading and oversize trucks. In order to observe the highway load character in Shaanxi province, truck weigh device is set up in highway pavement to measure axle weights and axle spacing. Based on these data, it can be classified and generalized the different classes of vehicles, and drawn out the simplifying fatigue truck model in Shaanxi province. Furthermore, the fatigue truck model was used to evaluate the fatigue life and service safety of typical concrete bridges.