To overcome the disadvantages of the traditional upstream dam-building method, an improved tailings dam-building method, i.e., upstream dam-building method using concentrated and classified tailings, is proposed. Based on the tailings dam model tests, and guided by the concentrated tailings technique, model tests of both the traditional and improved upstream dam-building methods were performed. Through these tests, the deposition condition and particle distribution of tailing materials were examined, and the variation of saturation line on dry slope was determined. The limit equilibrium method is used to calculate the minimum safety factors for different dam building methods. It is shown that: the building dam with highly concentrated tailings can lead to even particle distribution and obscure the particle classification, while reducing the inter-bed and fine-mud sandwiches in the sedimentary area; the improving upstream dam-building method favors the formation of a sedimentation type, which is good for drainage and flood control; the stability of tailing dam can be improved by 19% to 33% if the improved upstream dam-building method is adopted.