Because of advantages such as simple structure, ease of manufacture and high sensitivity, all-fiber interferometer has been applied in many sensing fields in recent years. In this paper, an all-fiber interferometer is proposed, which is based on a multimode fiber spliced between two single mode fibers with a certain of transverse offset. And it is applied for twist sensing. Experimental results show that the sensitivities are, through intensity interrogation method, -0.225 dB/(°·m) and 0.148 dB/(°·m) for measuring twist in clockwise and anti-clockwise directions, respectively. The sensitivities are, through wavelength interrogation method, -0.259 nm/(°·m) and 0.222 nm/(°·m) in twist directions of clockwise and anti-clockwise, respectively. The linearity, either using intensity or wavelength interrogations, is higher than 97% for the twist measurement from 0 to 180°. The proposed twist sensor has advantages of simple structure and good performance, making it a good choice for engineering applications, such as shape sensing and structural health monitoring. Furthermore, it can also be used for other measurements like temperatureand curvature.