Coal mining activities inevitably have some disturbance to the soil environment, which not only reflects on the changes of soil physical and chemical properties, but also has some influence on soil fauna groups. The depression produced by coal mining needs to be filled and reclaimed, and the fertility of the filled and reclaimed soil also needs to be restored by physical, chemical and biological measures to meet the needs of subsequent restoration. It is well known that earthworm is an important "engineer" of soil ecosystem, which has positive ecological functions on soil physical and chemical properties and soil fertility.

However, at present, the research on earthworm diversity in coal mining area is very scarce, and whether earthworm can improve the soil in coal mining area is unknown. Therefore, this study intends to study the diversity of earthworms in the soil of coal mining area and the improvement of reclaimed soil by earthworms, in order to investigate if the earthworm diversity could reflect the disturbance on the soil by coal mining activities, and at the same time, to explore whether earthworm can produce positive ecological improvement effect on the reclaim soil on the coal gangue. Through the field experiment, laboratory model experiment, soil column experiment and composting experiment, using physical, chemical and biological testing methods and technologies, combined with environmental science, biological science, biochemistry and ecology theories, the main conclusions are as follows: 1. The species number, population density, population diversity and evenness of earthworms in the old coal mining area are all lower than those in the new coal mining area and the control area, indicating that the coal mining can have some disturbance to the soil, thus reducing the earthworm diversity, and with the increase of coal mining time, the earthworm diversity decreased. 2. The EC, water content, organic carbon, total nitrogen, SMBC, SMBN, soil respiration intensity and heavy metals in different habitats (vegetable field, abandoned farmland, wood land and cropland) in the coal mine area are varied, and the overall soil environmental conditions are worse than those in non-mining areas. Soil moisture content, TN, SMBN, soil respiration intensity and heavy metals such as Pb and Zn in coal mining area can affect the characteristics of earthworm population. Soil respiration intensity and Zn are important environmental factors affecting the diversity of earthworm and earthworm population parameters. 3. The total and available contents of Pb, Cd, Cu, Zn in the soil of the mining area is higher than those of the control area (except the total Cu in the soil of Pani Coal Mine), and the total and available concentrations of heavy metals in the soil of Xinzhuangzi Coal Mine are higher than those of Pani Coal Mine, indicating that heavy metals increaseed with mining time in the soil around the coal mining area. At the same time, the amount of Pb, Cd and Zn absorbed by earthworms in soil increased with the increasing mining time, but the ability of earthworms enriching Pb, Cd and Zn decreased with the increasing the amounts of heavy metals in earthworm. 4. Inoculating earthworms in soil at 10-70cm soil thickness can significantly reduce the pH of soil overburden and make it neutral, and significantly increase the OM and TN of reclaim soil, but the effects of earthworm activity on TP and TK is not obvious. When the soil thickness was over 30cm, earthworm inoculation could significantly reduce the total amount of heavy metals and the contents of available heavy metals in the soil, especial for the total Pb and available Zn in the reclaim soil. Earthworm mainly changed TP to affect the contents of total Cr, total Pb and available Cr in soil, and mainly changed TN to affect the concentrations of total Cu, total Zn and available Cu, Pb and Zn in soil.