The smart geogrids installed with distributed fiber sensors can be used to both reinforce and monitor the stability of geogrid-reinforced slopes. In this paper, a geogrid-reinforced sand slope model was conducted in the laboratory. The fully distributed optical frequency domain reflectometry (OFDR) sensing technology was employed to measure the strain distribution of the geogrid embedded inside the model slope. Afterward, the surcharge loading was applied on the slope crest and the distributed fiber optic sensing data were collected under different stages. The monitoring results show that the fiber optical sensors can capture the progressive deformation of the geogrid-reinforced slope. Based on the model test, the performance of the reinforced soil slope is simulated by finite element software Plaxis2D as well. The strength reduction method was used to analyze the stability of the slope. An empirical relationship between the geogrid strain and the factor of safety was set up. The results indicate that the measured strain and calculated results agree very well. The strain of geogrid monitored by distribute optical fiber sensor can be used to evaluate the stability of geogrid-reinforced sand slopes.