In structural health monitoring, evaluation of bridge serviceability performance is based on vibration method. The vibration properties are influenced by temperature, humidity, wind and traffic load. Temperature differential in rigid frame bridge causes additional stress, which affects dynamic characteristics and induces concrete cracks. Thus analysis of temperature distribution is the basement of damage identification. Fiber Bragg grating (FBG) sensors are advanced materials for SHM. This paper introduces a temperature sensor monitoring system consisting of 52 temperature sensors on a twin-deck continuous rigid frame concrete bridge and analyzes temperature distribution on the twin decks of the bridge through August to December, 2006. Temperature at the same height sections differs little in the longitudinal direction along this bridge. The comparisons between maximum and minimum temperature each month reveal the asymmetry of transverse temperature distribution. The pavement has significant impact to the top slab temperature. In November the temperature declines sharply. The temperature on the external surface of top slab is lower than that of bottom for short box girders in winter because of shelters of flanges.