The length of dry beach is an important factor that influences the safety of tailings dams. However, there still is no accurate and reliable method that can conveniently measure the length of dry beach. In this paper, the authors focus on developing a novel method for dry beach length determination. The proposed method can effectively measure the dry beach length through an ordinary camera and four marking rods placed on the dry beach. Experimental results show that the proposed method can conveniently measure the dry beach length with high accuracy, and therefore it can be adopted as an effective method in tailings dam real-time health monitoring.