The mountain landslide has been the disaster which makes great harm in the nature. People have been looking for better monitoring of the preceding information to the landslide. A number of commonly used monitoring methods have been developed, but they have both advantages and disadvantages. With the development of optical fiber sensing technology, it is found that monitoring optical fiber has many advantages comparing with traditional methods. In this paper, the basic principal of optical fiber sensing technology is described; and technologies of optical power consumption, Optic Time Domain Reflectometry (OTDR), Brillouin Optic Time Domain Reflectometer (BOTDR) and Fiber Bragg Grating (FBG) are analyzed. A new composite optical fiber testing device based on optical fiber monitoring method is proposed. The device based on optical time domain reflectometry can achieve high initial accuracy, large range and direction of the judge.