Soil active organic carbon (AOC) fractions are good indicators of soil carbon stock change because of their rapid response to soil disturbances in natural ecosystems. Agricultural activities in the last 50 years have greatly influenced the soil organic carbon (SOC) of natural wetlands on Sanjiang Plain, China. The main objective of this study was to assess differences in the distribution of soil AOC fractions, including dissolved organic carbon (DOC), microbial biomass carbon (MBC), and easily oxidized organic carbon (EOC), and the main influencing factors in four different types of wetlands in the Honghe National Natural Reserve of Sanjiang Plain. The contents and allocation ratios of soil DOC, MBC, and EOC were investigated at three soil depths (0-10, 10-20, and 20-30 cm) in four types of wetlands: (1) a mixed Calamagrostis angustifolia and Salix brachypoda wetland (CSW), (2) a C. angustifolia wetland (CAW), (3) a Carex lasiocarpa wetland (CLW), and (4) a Phragmites australis wetland (PAW). The relationships among the three soil AOC fractions and soil nutrient contents (SOC, total nitrogen [TN], total phosphorus [TP]) and enzyme activity (sucrase, cellulase, and catalase) were also analyzed. The results showed that DOC, MBC, and EOC content gradually decreased with increasing soil depth in the 0-30 cm soil layer of all four wetlands. However, significant differences (P < 0.05) were noted for the soil AOC fractions among the four wetlands. The DOC, MBC, and EOC content was significantly higher in non-flooding CSW and CAW compared to long-term flooding CLW and PAW. In the four wetlands, the ratios of soil DOC, MBC, and EOC to SOC content at the three soil depths ranged from 0.27% to 0.63%, 1.27% to 5.94%, and 19.63% to 41.25%, respectively. In addition, the trend in the changes of soil DOC to SOC ratios initially increased, followed by a decrease along the soil profiles, with peak values being documented for the 10-20 cm soil layer. No specific trend was noted for MBC to SOC ratios, but EOC to SOC ratios decreased with soil depth. The highest DOC to SOC ratio was obtained for CAW, whereas the highest MBC and EOC to SOC ratios were obtained for CSW. In contrast, lower DOC, MBC, and EOC to SOC ratios were observed in the long-term flooding CLW and PAW. Furthermore, positive correlations were observed among DOC, MBC, and EOC in all four wetlands. Our results showed that DOC, MBC, and EOC content was strongly correlated with SOC, TN, and TP content as well as with the enzyme activity indicators in the four wetland soils, but no significant correlation was noted for the C/N ratio. A higher correlation coefficient was observed between these three AOC fractions with SOC and TN content. Furthermore, highly significant relationships were observed between DOC content and cellulase activity, as well as between MBC content and catalase activity. In conclusion, the soil AOC fractions were mainly influenced by soil nutrient content (SOC, TN, and TP) and enzyme activity, which are associated with the C cycle.