Abstract: Brillouin Optical TimeDomain Reflectometer(BOTDR)is a newly developed distributed fiber optic sensing technique. It has some unique functions such as distributed,long distance,antielectromagnetic interference,and waterproof. It is very suitable and useful to the monitoring and earlywarning of geological engineering such as slope engineering. However,poor strain coordination,fragility and difficulty for abnormal strain location are some of the problems for this technique to be applied to soil slope. In this paper,the BOTDR was applied to monitor the deformation of a small scale slope model built in laboratory. The fiber was attached to geotextile and geogrid. The two materials are very popular in slope treatment. They were emplaced in the fill slope at different depths while the slope model was being built. Microstrain of the slope deformation at varied loads were obtained with the BOTDR. By data processing and analysis,the abnormal deformation can be distinguished and its position can also be identified．