Abstract: Double-layered suspen-dome structure was applied in Tianjin Sports Center Velodrome． Temperature and strain monitoring was carried out to guarantee the safety and to study the mechanical characteristic and temperature distribution of the dome． Temperature of members was measured by thermocouple method and strain of the key members by vibration wire strain sensor． A great number of data of temperature and stress distribution were obtained during monitoring． By analyzing these data，it is shown that strain change under ordinary situation is largely caused by temperature change in steel structure especially long-span space structure． Member temperature is coincides with environment temperature，which means the daily maximum temperature could be taken as the highest temperature of structure and actual temperature in the building could be lowest temperature of structure when heating is guaranteed in winter．