Non-coal mining generally produces a large amount of tailings, and tailings usually accumulate in the canyon between two mountains, and the downstream of the tailings is intercepted by the dam. The dam is called a tailings dam. The development of safety monitoring technology for tailings dam is accompanied by the history of dam construction. The safety of tailings dam is not only related to the normal operation of mining industry, but also to the life safety of downstream residents. Once the tailings dam break, the loss caused by the dam is inestimable. In this paper, the laser collimation system is used to monitor the displacement of the dam, and the center of light is measured by the center of gravity, and the laser beam is reconstructed by a lens. The method has the advantages of high accuracy and simultaneous detection of horizontal displacement and vertical displacement of tailings dam. It is a new monitoring technology for dam displacement and has good application prospects.