Because stage cable-bridge have long spans and large members, their movements and geometrical changes by temperatures tend to be bigger than those of small or medium-size bridge. Therefore, it is important for maintenance engineers to monitor and assess the effect to temperature on the cable-supported bridges. To evaluate how much the superstructure expands or contracts when subjected to changes in temperature is the first step for the maintenance. Thermal movements of a cable-stayed bridge in service are evaluated by using long-term temperatures and displacements data.