【Objective】Microbial biomass carbon(C)metabolism is vital in the formation and stabilization of organic C in soil, constituting a critical parameter in the models of terrestrial ecosystems. Yet, the variances in the microbial C metabolism indices in soils developed from different lithological origins remain undefined. 【Method】To address the scientific gap in the characteristics and driving factors of microbial biomass C metabolism in soils developed from different rocks, we sampled forest soils developed from limestone and clastic rocks as research objects. Using ¹⁸O-H₂O labeling, we measured the microbial growth rate, respiration rate, carbon use efficiency (CUE), and turnover time. Combined with soil physicochemical properties, soil organic matter mineral protection characteristics, soil enzyme activity, and microbial biomass and community composition, we clarified the influencing mechanism of lithology on forest soil microbial biomass C metabolism. 【Result】The findings indicate that the pH and the 0.002～0.05 mm particle content in limestone-derived soils surpass those in clastic rock-derived soils, whereas soil organic carbon (SOC), total nitrogen (TN), dissolved organic carbon(DOC), C: P and N: P ratios were lower in limestone-derived soils (P<0.05). The limestone-developed soils had a higher content of exchangeable calcium and magnesium (Ca/Mg) and free iron and aluminum ((Fe+Al)_d) than the clastic rock-developed soils, but the content of amorphous iron and aluminum((Fe+Al)_o)was lower than that in the clastic rock-developed soils. Furthermore, the enzyme activity related to C, N, and P cycling in limestone-developed soils was significantly lower than that in clastic rock-developed soils (P< 0.05). In addition, the microbial biomass phosphorus (MBP) in limestone-developed soils was higher than that in clastic rock-developed soils, but microbial biomass carbon(MBC), fungi: bacteria ratio (F: B), and Gram-positive to Gram-negative bacteria ratio (G⁺: G^-)were significantly lower than those in clastic rock-developed soils (P<0.05). The microbial growth rate and turnover rate in limestone-derived soils were significantly higher than in clastic rock-derived soils (P<0.05), but there was no significant difference in the microbial respiration rate and CUE between the two types of soils. Correlation analysis revealed that the soil microbial growth rate and turnover rate were significantly positively correlated with soil pH, (Ca+Mg): (Fe+Al)_o, (Ca+Mg): SOC, (Fe+Al)_d: SOC, and Gram-negative bacteria(P<0.05), and significantly negatively related to DOC, organic C bound to iron and aluminum, enzyme activity, MBC: MBN, F: B, and G⁺: G^- ratio(P<0.05). The soil CUE was significantly negatively correlated with MBC and MBC: MBN (P<0.05) while microbial respiration rate was only significantly negatively correlated with phenol oxidase activity (P<0.05). In summary, the higher pH, weaker amorphous iron-aluminum mineral protection, lower microbial resource limitation, and larger bacterial biomass (especially Gram-negative bacteria) in limestone-derived soils may lead to greater microbial motility in these soils and stronger substrate availability, resulting in larger microbial growth and turnover rates. However, there was no difference in the soil microbial biomass CUE between the two rock types, which may be due to the similar soil C: N ratio. 【Conclusion】The microbial biomass C metabolism of forest soils developed from two types of rocks is controlled by biological and non-biological factors. These research results provide a new mechanism for explaining the differences in organic carbon pools in forest soils developed from different rocks.