In this paper, a bending sensor based on microstructured fiber is proposed. The fiber sensor is in-line, all-fiber and distributed sensing. Especially, by contrast to the bending sensors which based on multicore microstructured fiber, it is immune to the bending directions and has good repetition along different directions. Thus it is convenient to be buried into the materials or structures without considering the radial orientation. The sensor is suitable for practical application and to monitor the bending radius of the structure. The other potential application of the sensor is that it may transport the healing materials in its hollow core.