In order to further promote carbon sequestration and fertilization in Phyllostachys violascens forest, the effects of biochar with nitrogen fertilizer on soil nutrient content, carbon and nitrogen transformation-related enzyme activities, and microbial carbon and nitrogen utilization efficiencies were investigated through a field experiment in 2019. The experiment was set up with three biomass charcoal gradients B0, B1, B2 at 0, 10, 30 t/hm2, respectively, and three nitrogen fertiliser gradients N0, N1, N2 at 0, 0.5, 1 t/hm2, respectively, for a total of nine treatments (B0N0, B0N1, B0N2, B1N0, B1N1, B1N2, B2N0, B2N1, and B2N2). The results showed that biochar and nitrogen fertilizers significantly enhanced soil organic carbon, total nitrogen, ammonium nitrogen, and available phosphorus contents, and there was also a significant interaction effect between the two (except for soil available phosphorus), and soil organic carbon and soil nutrient contents were the highest under the B2N1 and B1N1 treatments in general. Microbial biomass carbon, nitrogen content and β—glucosidase activity were highest in the B2N1 treatment, with a significant increase by 65.1%, 293.1% and 59.6% over the B0N0 treatment. Microbial phosphorus content, N—acetylamino glucosidase and leucine aminopeptidase activities were highest in the B2N2 treatment with a significant increase by 193.3%, 119.6% and 64.0% over the B0N0 treatment. Soil microbial carbon utilization efficiency (CUE) was significantly positively correlated with soil total nitrogen, soil organic carbon, nitrate nitrogen, ammonium nitrogen, available phosphorus and microbial carbon and nitrogen (P < 0.01). Soil organic carbon, microbial carbon and nitrate nitrogen had the highest explanatory rate for CUE. Soil microbial nitrogen utilization efficiency (NUE) was significantly negatively correlated with soil microbial biomass nitrogen (P < 0.01), and soil microbial biomass nitrogen, soil organic carbon and ammonium nitrogen had the highest explanatory rate for NUE. Overall, the increase of CUE and the decrease of NUE under biochar with N fertilizer indicated that soil microbial sequestration of carbon increased mineralization of nitrogen enhanced in Phyllostachys violascens forest. Therefore, the application of biochar can be a potential measure for carbon sequestration and fertilization and land enhancement, but the long-term effects of biochar with N fertilizer on soil microbial communities are not clear, and the further research is still needed.