Abstract: Ensuring the safety of concrete faces is the key to the safe operation of concrete face rockfill dams (CFRDs). The deflection is an important index to monitor the integrity of a concrete face. Based on the distributed optical fiber sensing technology, a new technology is proposed to monitor the deflection of concrete faces of CFRDs, and systematic tests are carried out to verify the measurement accuracy of this new technology as well as its feasibility. Based on the Matlab program and the quasi-distributed scatter strain test data, a method for calculating deflection is established. The research findings show that the calculated deflection at each measurement point on the concrete face is consistent with the measured one at the corresponding position (the absolute error is 5 mm, and the average relative error is 3%). It is validated that this new technology can monitor the deflection including irregular deflection with millimeter accuracy. It is also suitable for the distributed monitoring of the deflection of the full section of concrete faces and the measurement of large deflection. The proposed advanced technology is proved to be applicable to monitoring the deflection of the entire concrete face of a 300-meter level CFRD in a distributed manner.