In this study, the data of soil dissolved organic carbon (DOC), microbial biomass carbon (MBC) and related environmental factors under nitrogen addition conditions were collected from a total of 86 literatures, and 1 910 pairs of observation data were obtained to quantify the responses of soil DOC and MBC to nitrogen input and their potential driving processes by the method of meta analysis. The results showed that nitrogen input significantly altered soil chemical properties, promoted the increases in plant aboveground and underground biomass, and significantly reduced soil microbial biomass (including fungi, bacteria, and actinomycetes). The responses of soil DOC and MBC to nitrogen input were not consistent. Nitrogen input significantly increased soil DOC (7.48%) and significantly reduced soil MBC (4.03%). With the increase of accumulated nitrogen input at the experimental site, soil DOC significantly increased but soil MBC significantly decreased. The results of random forest prediction indicated that aboveground biomass and soil pH were the most important predictive factors for DOC under nitrogen addition conditions, while soil pH, total microbial biomass, and fungal biomass were the most important predictive factors for MBC. In summary, the increase in soil DOC under nitrogen input conditions was mainly related to the increase in plant-based carbon input, while the decrease in soil MBC was due to the inhibitory effect of nitrogen enrichment on microbial growth, which was related to a significant decrease in soil pH. And the different driving pathways of nitrogen input on soil DOC and MBC were the fundamental reasons for their differentiated responses.