Environment conditions such as temperature, humidity, traffic loadings and wind loadings cause changes in the identified dynamic properties of bridges, which will affect health diagnosis based on the mode frequencies in bridge structural health monitoring. This paper analyzed temperature effects on a rigid continuous bridge based on monitoring data from Aug. 2006 to Dec. 2006. First, temperature data calculating process from measured data is given and frequency time histories are graphed. Temperature effects on the bridge dynamic properties are divided into yearly temperature change and sunlight radiation. Then, theoretical eigenfrequency functions of a simply-supported uniform beam with and without axial force are provided to explain and distinguish temperature effects and constraints on characteristic frequencies. Relationship of measured temperature and frequencies data are drafted and linear correlations are found on the 1st and 3rd vertical frequencies. 2nd vertical frequency fluctuated cyclically in one day, caused by sunlight radiation and restrains.© (2011) COPYRIGHT Society of Photo-Optical Instrumentation Engineers (SPIE). Downloading of the abstract is permitted for personal use only.