Fiber Bragg grating (FBG) is a new type of monitoring and sensing element with advantages of high accuracy, strong anti-interference ability, and real-time monitoring. A USTX-2000 loading device was applied using FBG sensors to evaluate the mechanical properties of a geogrid-reinforced embankment and monitor the deformation characteristics of the reinforcement under cyclic loads. A series of model tests were performed under different conditions, such as different reinforced layers and reinforced spacings. The test results showed that the geogrid strain decreased from the centre direction of the loading plate to both sides in the horizontal direction and was non-linearly distributed in the longitudinal direction of the geogrid. The geogrid strain decreased with an increase in the embankment depth in the vertical direction for the same condition under long-term dynamic loads. The reinforcement could effectively reduce the settlement of the embankment and the normal deformation of the slope, and the earth pressure in the embankment significantly increased with the reinforcement. The study demonstrated the feasibility and superiority of FBG new sensing technology in embankment slope monitoring.