Coal mining can lead to coal spontaneous combustion, especially in arid and semi-arid areas, and soil can suffer varying degrees of depletion and degradation, which can be harmful to the regional eco-environment. However, the characteristics of soil depletion and degradation are not yet clear in the coal fire areas, and there are fewer soil quality assessments. In this study, we studied the characteristics of soil ions, nutrient and their stoichiometric ratios at different sampling points and different thermal effects. The principal component analysis and membership function were used to calculate the soil quality index (SQI) to comprehensively evaluate the impact of different thermal effects on soil quality (SQ). The results showed that soil cations were dominated by Na+ and anions by Cl- and SO42-, and the higher the temperature, the higher the concentration of SO42-. The concentrations of Na+ and Cl- tended to increase with increasing temperature, while the opposite was true for K+ and SO42-. Soil organic carbon (SOC) increased with increasing temperature, Total nitrogen (N) content was lower when heated at 40 degrees C 5 d, and the N:P ratio was 8.99. The degree of soil degradation at this time was only lower than that at 70 degrees C for 10 and 20 d, which indicated that the SQ was initially affected by the temperature. The analysis using principal component analysis and membership function showed that the Sikeshu (SKS) fire area (SQI = 0.183) was lower than the Wugong (WG) fire area (SQI = 0.281). In the homemade heating experiment, the SQI of the soil affected by thermal effects was lower than that of the raw soil. The SQIs were consistent at 40 degrees C 20 d and 70 degrees C 10 d, indicating that the effect of low temperature for a long time and high temperature for a short time on SQ can be equivalent. The results of this study provide a theoretical basis for SQ improvement and ecological restoration in coal fire areas.