In order to investigate the relationship between soil microbial diversity and soil carbon metabolism, this study used gradient dilution method to modify the diversity of the original soil microbial community(the dilution of 10^-1, 10^-3 and 10^-5 times for treatments of D1, D3 and D5, respectively). Six weeks of pre-culture experiment was carried out to eliminate the effects of gradient dilution on microbial community abundance in soils. To evaluate the results of pre-culture experiments, the bacterial abundance and gene diversity index (ACE, Chao1 and Shannon) were determined by the Q-PCR and high-throughput sequencing, respectively. Thereafter, the same amount of glucose (0.5 g/100 g dry soil) was added in the culture, and the carbon mineralization rates of the three treated soils were measured during the incubation period. The Biolog ECO plate experiment was performed to analyze the functional diversity index (Shannon Index (H), Simpson index (D), and McIntosh index (U)) and carbon source metabolic intensity of bacteria in each soil sample. The results showed that the soil carbon mineralization rates and cumulative carbon mineralization were the greatest in D1 treatment, followed by D3 and D5. The average well color development (AWCD), H and U were significantly higher under D1 treatment than those under D3 and D5 treatments (P<0.05). Principal component analysis for 31 kinds of carbon sources also indicated that the patterns of carbon source utilization of the three treatments were different, and the effect of soil microbial community on carbon source utilization under D1 was more significant than that under D3 and D5 (P<0.05). Taken together, this study showed that the decreases of soil microbial diversity would alter the soil carbon metabolic intensity and mineralization processes.