In the pot experiment, coal gangue and coal slurry were added with different mass ratios to the soil collected from Horqin Sandy Land, and alfalfa (Medicago sativa L.) was used as the tested plant. Soil chemical properties, the contents of microbial biomass carbon (MBC), nitrogen (MBN), and phosphorus (MBP) were measured, and soil integrated fertility index (IFI), microbial stoichiometric ratios, microbial entropy (qmb) and its stoichiometric imbalance were calculated. The relationship between microbial dynamics and soil nutrient metabolism was explored through correlation analysis and redundancy analysis. The results showed that compared with the treatment without adding coal gangue and coal slurry (CK), soil IFI, MBC, MBN, and MBP all were significantly increased under the combined application of coal gangue and coal slurry. Among them, the treatment with 10% coal gangue and 15% coal slurry had the highest IFI, MBC, MBN, and MBP, increased by 28.13%, 173.44%, 112.09%, and 404.35%, respectively compared with CK; soil microbial entropy carbon(qmbc), soil microbial entropy nitrogen(qmbn), and soil microbial entropy phosphorus(qmbp) qmbp were also significantly increased compared to CK. There were significant differences in the changes of soil microbial stoichiometry ratios and soil microbial stoichiometry imbalance between different treatments. Correlation analysis showed that MBC, MBN, and MBP were significantly (P<0.05) or extremely significantly (P<0.01) positively correlated with qmb and soil IFI. Redundancy analysis showed that qmb was influenced by soil microbial stoichiometric ratios and its stoichiometric imbalance, with soil nitrogen phosphorus imbalance ratio (N/Pimb) and soil carbon nitrogen ratio (SOC/TN) being the main factors affecting qmb, explained 42.5% (F=20.7, P=0.002) and 38.0% (F=52.7, P=0.002) of soil qmb, respectively, and being key factors drove soil microbial entropy. In conclusion, the combined application of coal gangue and coal slurry can significantly change in the differences between soil microorganisms and resource chemical components, thus improving soil fertility.