Modal analysis is an important tool for structural health monitoring based on measured acceleration data, which affects the result of damage identification, safety evaluation and prediction. This paper starts with a brief review of modal identification methods, and then introduces a rigid continuous bridge-Dongying Yellow River Bridge (DYRB) and its structure health monitoring system. Amounts of acceleration data was collected from August to December 2006. The peak picking method is adopted and enhanced with selected accelerometers using average and fitting methods. As a result, the 1st transverse and first 3 vertical frequencies were identified accurately and efficiently. More researches are needed to analyze the different appearance of different mode frequencies and to verify the influence of temperature, moisture, wind, traffic load, etc.© (2011) COPYRIGHT Society of Photo-Optical Instrumentation Engineers (SPIE). Downloading of the abstract is permitted for personal use only.