The orientation change of nematic liquid crystal (NLC) can be used in biosensor. The sensing characteristics of side-polished fiber (SPF) for measurement of NLC orientation are investigated. The relationship between the theoretical formula of liquid crystal refractive index and the optical transmission power in SPF is derived by empirical approach. The mechanical rotating method is designed to change the orientation of NLC on the polished surface. Experimental results show that the orientation variation of liquid crystal can indeed be used to monitor the output optical power transmitted through the SPF. With mechanical rotation method, when the rotation angle increases from 0° to 90°, the output optical power increases by 28.10 dB. With in the angle range from 0° to 30°, the response is almost linear. The average response slope is about 0.359 dB/(°), which indicates relatively high sensitivity. Experiments indicate that SPF can be used to measure the orientation variation of NLC, and the variation range is also obtained. The work provides a reference for a new fiber optical biosensor based on the SPF and NLC.