The principle and advantage of polarization-optical time domain reflectometry (POTDR) are illustrated.Some typical modulation effects related to POTDR distributed optic fiber sensors are introduced,which include electro-optical effect,Faraday effect and elasto-optical effect,etc.Distributed optic fiber sensors based on POTDR plays an important role in state-of-the-art monitoring system.On the other hand,its further development faces challenges due to some technical problems.The possible future directions for the development of POTDR distributed optic fiber sensors are also analyzed.