To reveal the effects of nitrogen and phosphorus addition on soil microbial characteristics, an old-growth evergreen broadleaved forest in the Xianyu Mountains in Chizhou of the Anhui Province was selected. Four treatments of nitrogen and phosphorus addition were designed, including a control (CK, 0 kg N/hm²), low nitrogen (LN, 50 kg N/hm²), high nitrogen (HN, 100 kg N/hm²), and high nitrogen + phosphorus (HN + P, 100 kg N/hm² + 50 kg P/hm²) treatments. Microbial biomass carbon (MBC), biomass nitrogen (MBN), and microbial community functional diversity for different soil layers (0-10 cm, 10-20 cm, and 20-30 cm) were analyzed using the methods of chloroform-fumigation and the Biolog system. The results showed that MBC and MBN decreased with soil depth, with significant differences among soil layers (P > 0.05). The MBC and MBC/MBN ratio changed significantly after N and P addition. The metabolic activity of the soil microbial community also declined with soil depth. Soil microbial activities were highest in the HN and LN treatments. McIntosh, Shannon, and Simpson diversity indices differed in different soil layers and at different dosages of N and P. Microbial diversity indices for the 0-10 cm soil layer were significantly different among treatments. Carbon source utilization by soil microbes was highest for carboxylic acids, amino acids, and carbohydrates. The results of principal component analysis showed that carbon source utilization was different among the soil layers. There was significant spatial variability in carbon source utilization in the upper 0-10 cm of soil under different N and P treatments, whereas it was relatively stable in other soil layers (10-30 cm). This spatial heterogeneity was mainly manifested in carbon source utilization of carbohydrates and carboxylic acid. In general, the soil layer and N and P treatments had significant impacts on MBC, MBN, and soil microbial functional diversity, with greatest impacts occurring on the surface soil with high N treatment.