A high sensitivity optical fiber curvature sensor with a fiber structure is proposed based on single mode-polarization maintaining-single mode (SPS), which is fabricated by splicing a piece of polarization-maintaining fiber (PMF) between two sections of single mode fiber. The curvature sensing performance and the effect of the length of PMF on the curvature sensitivity of this sensor are studied in experiments. The results show that, the output spectrum of this sensor shows an obviously red-shift phenomenon with the increase of curvature. In addition, the length of PMF has a significance influence on the curvature sensitivity of this sensor. In the curvature range from 0.43 m -1 to 1.37 m -1, the maximum sensitivity can reach to 59.849 nm/m -1 when the length of PMF is 11 cm. This sensor has advantages of simple structure, easy fabrication and high sensitivity compared with the other optical fiber sensors with an optical fiber structure, and it can be used in the field of the structural health monitoring.