[Objective] Soil labile organic carbon (LOC) is a soil component that is quite quick in turnover and quite sensitive to soil management practices. However, it is not clear how application of organic materials or manures LOC and their microbial mechanisms.[Method] In this study, a field experiment was designed to have wheat and maize planted in rotation and conducted to explore effects of returning wheat straw (R) and applying woody peat (MT) for two years in a row on potential carbon mineralization (PCM), microbial biomass carbon (MBC), dissolved organic carbon (DOC), readily oxidizable carbon (ROC) and particulate organic carbon (POC) in fluvo-aquic soil at the harvesting stage of the second maize crop.[Result] Compared with CK without any organic manure, Treatment R (returning of wheat straw) and Treatment RMT (returning of wheat straw plus application of wood peat) was 30.33% and 31.46% higher in DOC and 104.86% and 64.78% higher in POC, respectively. However, the treatments did not have much effect on PCM, MBC and ROC. High-throughput sequencing analysis shows that the treatments did not have much impact on soil bacterial community composition, but did have on fungi, which was mainly attributed to changes in POC, DOC and . Correlation analysis shows that DOC and POC were significantly and positively related to invertase activity. Both DOC and invertase increased significantly in Treatment R and were significantly and positively related to the abundance of Ttrichoderma peltatum and Trichoderma aerugineum. At the same time, DOC was significantly and positively related to the abundance of Pyrenochaeta unidentified, capable of promoting formation of root secretions, and Pyrenochaeta unidentified increased significantly in Treatment RMT. Both POC and invertase were significantly and negatively related to Cladorrhinum flexuosum and Basidiobolus ranarum, both of which decreased significantly in Treatment MT, while only Cladorrhinum flexuosum did in Treatment RMT. POC and invertase were also significantly and positively related to Chaetothyriales unidentified, and increased significantly in Treatment RMT.[Conclusion] All the findings demonstrate that both returning of wheat straw and application of woody peat alter the content of labile organic carbon, regardless of type, which may be attributed to the effects of the two practices affecting, separately, composition of the fungal community, thus altering abundance of the functional microbes and activity of relevant enzymes.