In view of the flaw that the traditional fatigue life assessment method of steel deck of suspension bridge fails to take into consideration the influence of temperature load, a fatigue durability assessment method has thus been proposed of the steel deck of suspension bridge with the coupling effect of vehicle-temperature loading under consideration. Taking Nanxi Yangtze River Bridge as the target of the engineering background, and based on the vehicle weight in motion (WIM), U-rib detail strain, pavement temperature and ambient temperature monitoring data of suspension bridge girder, an establishment can be achieved of the standard fatigue vehicle model, pavement temperature probability model and girder temperature difference model. By adopting ANSYS finite element platform, a transient analysis has been made of the calculation of the influence of vehicle and pavement temperature load coupling on the fatigue stress effect of two typical welding details, with the fatigue stress spectrum of structure temperature recorded. On this basis, a prediction can be achieved of the fatigue life of two typical details of Nanxi Yangtze River Bridge under vehicle-temperature load coupling. The results show that there is a linear relationship between the temperature of asphalt pavement and the equivalent stress amplitude under the condition of the same vehicle load, with the effect of temperature on the fatigue life of details decreasing with the increase of the distance between details and pavement. The number of cycles of the temperature gradient fatigue load spectrum is significantly smaller than that of the vehicle load spectrum, while the contribution of the vehicle load to the fatigue damage plays a dominant role in the coupling effect. Based on a comparison between the coupling effect with or without the vehicle temperature load taken into consideration, the calculated fatigue damage values of detail 1 and detail 2 of Nanxi Yangtze River Bridge are 5.06 and 1.50 times respectively after 100 years of service.