Abstract: Large Dam Safety Supervision Center of State Electricity Regulatory Commission Optical fiber distributed strain sensing (OFDSS) based on BOTDA/R is a supplementary method to traditional sensors. This new monitoring technique provides a comprehensive and efficient approach for structure health checkup and projects operation state evaluation, which helps diagnose the location and degree of defects timely and then warn before disaster. OFDSS has been used successfully in some large infrastructures and is very promising for hydraulic structure monitoring such as diversion tunnel, surge chamber, spiral case, dam body, etc.