This paper illustrates the principle of several common distributed fiber sensing techniques, especially Brillouin optical time domain reflectometry (BOTDR) and optical time domain reflectometry (OTDR). By measuring the frequency shift of spontaneous Brillouin scattering light in fiber, BOTDR could simultaneously monitor both strain and temperature with a high spatial resolution. But the spontaneous Brillouin scattering signal is so weak that it has a high demand of the laser generator and the signal-to-noise ratio of the whole system. Therefore, the BOTDR system is usually too complex, expensive and difficult to be widely used. Unlike BOTDR, OTDR utilizes Rayleigh scattering to measure the loss of fiber. Rayleigh scattering signal is much stronger than spontaneous Brillouin scattering signal, thus OTDR system has the advantages of high sensitivity, long distance and relatively low price. These advantages make OTDR very suitable for wide application in the field of slope monitoring, especially in remote areas where the geographical environment is complex and are difficult for staff to stay. <p> </p>This paper designed and implemented a slope monitoring and warning system based on the technology of optical time domain reflectometry(OTDR). The test result shows that the system has high sensitivity, strong real-time and provides user friendly interface.