AbstractUnderstanding the process of changes in substrate physical, chemical, and biological properties is critical for vegetation ecosystem reconstruction of open‐pit coal mining dumps. However, the relationships of soil chemical, biological, bacterial, and fungal characteristics in open‐pit coal mining dumps in grassland area are still unclear. The purpose of this study is to understand the changes and relationships of soil physic‐chemical, bacterial, and fungal properties under the reclamation time series of open‐pit coal mining dumps. Soil samples were collected from the waste dump reclaimed after 2, 5, 10, and 15 years in Shengli West No. 2 open pit coal mine in Inner Mongolia, China, and the surrounding natural grassland was set as a control at 0–10 cm and 10–20 cm. Soil pH, electrical conductivity (EC), soil organic matter (SOM), nutrient properties, bacterial, and fungal community structures were measured in the waste dump reclaimed after 2, 5, 10, and 15 years. The results showed that soil pH was decreased at 0–20 cm in the waste dump while SOM was increased by 1.2 times in 0–10 cm reclaimed after 15 years than that after 2 years. Soil EC was decreased by 55.5% and 58.3%, respectively, in 0–10 cm and 10–20 cm, respectively, after 10 years than that after 2 years. Soil available nitrogen, available phosphorus, and available potassium were 97.8%, 13.2%, and 60.9% lower after 15 years' reclamation than those in control. The acid phosphatase in 0–10 cm and 10–20 cm was increased by 2.2 and 2.1 times, respectively, after 15 years compared with that after 2 years. Alkaline phosphatase was decreased by 16.8% reclaimed after 15 years than that after 2 years in 10–20 cm soil. The Shannon diversity index of fungi was increased by 42.0% and 43.8%, respectively, in 0–10 cm and 10–20 cm, in the waste dump reclaimed after 15 years than that after 2 years. Soil organic matter was positively correlated with soil urease activity. Soil pH, EC, and texture had different effects on bacterial and fungal communities. Therefore, appropriate measurements should be applied to the reclamation dumps to help the soil properties of reclamation areas to recover to the natural grassland.