A new type displacement sensor based on few-mode multi-core fiber is presented. The sensor consists of two segments of single mode fiber and a segment of few-mode multi-core fiber. The sensing principle of the sensor is investigated and the experiments are performed to verify its feasibility. The experimental results show that the sensitivity of this sensor is -61.17 pm/μm with the elongation from 0 to 60 μm, error between the experimental results and the theoretical calculation is less than 3.9%. So the minimum change of displacement detected is 17 nm by using an optical spectrum analyzer (OSA) with high resolution.