Soil organic carbon decomposition is one of the key processes in soil carbon cycling,and regulated by input of exogenous carbon through influencing microbial community composition and enzyme activity,which is defined as priming effect. However,how the quality and input method of exogenous carbon influences priming effect in forest soils with different fertility remains unclear. In this study,two soils with different properties (poor and fertile) from Chinese fir forests were collected as rearch subjects,and ¹³C-labeled Chinese fir litter and glucose solution were added. The Chinese fir litter was added to the soils using two methods: placing intact litter on soil surface (IL) and uniformly mixing litter powder into soil (CL). The amount of CO₂ released from the soil and its ¹³C isotopic value were measured during 120-day incubation,and soil nutrient content and microbial community structure were also measured. The results showed that: (1) the input of intact litter resulted in a negative priming effect,while glucose addition induced the positive priming effect. They had significant impact on the cumulative primed carbon and the intensity of the effect is signally regulated by soil nutrients. As the same time,the cumulative primed carbon by intact litter addition and glucose addition were -1.22 mg C/g SOC and 4.80 mg C/g SOC in poor soil,respectively,and were -1.73 mg C/g SOC and 1.56 mg C/g SOC in fertile soil. (2) Compared to placing intact litter on soil surface,mixing litter powder into the soil caused positive priming effect (2.21 mg C/g SOC) in poor soil,but negative priming effect (-1.72 mg C/g SOC) in fertile soil. (3) Compared with the control treatment,exogenous carbon input significantly increased soil carbon-acquiring enzyme (36.1%),nitrogen-acquiring enzyme (88.6%) and phosphorus-acquiring enzyme (21.4%) in both Chinese fir forests. (4) Soil bacterial biomass significantly differed between two addition methods of litter in both soils (P < 0.01),with biomass being 27.0% greater under litter powder addition than intact litter addition in poor soil and 19.2% greater in fertile soil. (5) Cumulative primed carbon was positively correlated with soil enzyme activity related to nitrogen cycling,and negatively correlated with soil bacteria biomass. In summary,the quality and addition method of exogenous organic carbon affects the priming,which is regulated by soil property,especially microbial community composition and enzyme activity. These results provide theoretical support for managing soil organic carbon in subtropical Chinese fir forests.