In order to achieve accurate optical measurement method in micro-displacement and improve the accuracy of micro-displacement, we propose a novel micro-displacement optical fiber sensor based on surface plasmon resonance. In order to achieve precise measurement of micro-displacement, we use the characteristics that the propagation angle of the beam in the graded-index multimode fiber changes with the position of the incident light, and the resonant wavelength of the surface plasmon resonance sensor has the high sensitivity to the resonance angle variation. In order to achieve the resonance conditions, we polish the graded-index multimode fiber into a wedge with a suitable angle and precisely control the length of the graded-index multimode fiber. In addition, the fiber probe should be immersed into liquid such as water. A white light source is coupled from the end face of the graded-index multimode fiber to the fiber probe via a 630 nm single mode fiber, and an optical spectrum analyzer is employed to collect light beam and process the sensing signal. The fiber probe and single mode fiber are placed in a high precision displacement platform to control the radial relative position of the fibers. The experimental results show that when the fiber polishing angle is 12° and the liquid refractive index is 1.350, the micro-displacement optical-fiber sensor has a maximum sensitivity of 10.32 nm·μm -1 and a minimum resolution of 1.9 nm.