【Objective】The thickness of soil cover is a key factor determining the ecological restoration effectiveness of the open-pit coal mine dump. A reasonable reclamation thickness directly affects the effects of soil erosion control, nutrient retention, and vegetation restoration.【Method】Taking the dump of Fushun West Open-pit Mine as the research object, a platform-slope model with a height of 50 cm, a platform width of 40 cm, and a slope of 25°was constructed. An indoor simulated rainfall test was conducted, and the rainfall duration was 120 min. During the rainfall process, to record the development process of the rill, one section was taken along its longitudinal direction at the top, middle, and bottom, respectively. The width and depth of the trench were measured with a steel ruler, and the length of the trench was recorded simultaneously. The average values were respectively taken as the morphological characteristic parameters of the rill. The measurement time was from the beginning of the self-generated flow. Within the first 20 min, measurements were taken every 2 min, and from 20 to 120 min, measurements were taken every 6 min. Meanwhile, the runoff and sediment yield were collected every two min using the runoff bucket. After 12 h of sedimentation, the supernatant was collected, and the flow rate was measured with a graduated cylinder. The sedimentary soil was dried in an oven at 105℃ to a constant weight, and the moisture content was measured. Afterwards, the runoff volume was estimated as the sum of the water volume measured by the graduated cylinder and the soil moisture content, while the sediment yield was considered as the dry weight of silt and sand. After determining the sediment yield, nutrient con-tent analysis was conducted. Soil organic matter was determined by the potassium dichromate external heating method, total nitrogen was determined by the Kjeldahl nitrogen analyzer method, and available phosphorus and available potassium were determined by ICP-MS. By analyzing the obtained data, the influence mechanism of different soil cover thicknesses on the sediment yield characteris-tics and nutrient loss process of the waste dump was revealed.【Result】(1) Under different soil cover thicknesses, rill erosion was dominant. The process can be divided into the rill head formation stage, the rill erosion development and evolution stage, and the stable stage. The maximum development rates were 0.65-3.0 cm∙min-1, 1.5-16.75 cm∙min-1, and 0.38-1.25 cm∙min-1, respectively. The soil cover thickness was linearly and positively correlated with the time of the maximum sediment yield rate and the time of the maximum sediment content, with R2≥0.93. That is, increasing the soil cover thickness can effectively delay the occurrence of erosion and reduce the output of sediment. (2)Also, the rate of soil nutrient loss decreased with the increase in soil cover thickness. Under the conditions of 10 cm, 20 cm, and 30 cm soil cover, it was 4.34%-55.11%, 4.97%-46.78%, and 2.61%-40.93%, respectively. The overall degree of nutrient loss followed available phosphorus > total nitrogen > available potassium > organic matter. (3) The dynamics of nutrient loss and the rate of sediment yield and flow showed a synergistic change pattern. The cumulative contribution ratios of sediment yield and flow in the first, second, and third stages of erosion ditch development were 2.3%-3.4%, 55%-71%, and 31%-43%, respectively, and the cumulative contribution ratios of sediment yield were 0.7%-3%, 47%-88%, and 13%-52%, respectively. Additionally, the contribu-tion ratios of cumulative nutrient loss were 0.61%-4.8%, 35.10%-81.48%, and 14.48%-63.98%, respectively. The second stage of fur-row development was the main stage of sediment yield and nutrient loss, but the peak loss rate was delayed with the increase of soil cover thickness.【Conclusion】Based on the goal of controlling soil erosion and nutrient loss, it is recommended that in the reclamation project of dumps under similar climate-soil conditions, the soil cover thickness be set at 30 cm.