Forest litter is the main source of dissolved organic carbon (DOC) in forest ecosystem and plays an important role in the process of ecosystem carbon cycle. In this study, the litter of Juglans mandshurica, Larix gmelinii and their mixed plantation in Maoer Mountain were taken as research objects. The high-efficiency cellulose degrading fungi Peniophora intranata and Sarocladium strictum were made into single (agent A, agent B) and mixed fungal agent (agent C) by liquid fermentation culture. The DOC content of forest litters treated with agents in different periods under field conditions was measured. The effects of degrading agents on the dynamic changes of DOC content of different types of litters were analyzed, and the similarities and differences of degradation modes of each litter substrate were compared. Results showed that DOC contents of the three litter substrates showed a downward trend with the increase of degradation time after treatment, and the decreasing range was in the order of mixture > J. mandshurica > L. gmelinii. In the first month, the DOC content of each litter substrate was significantly higher than that of other degradation periods. The DOC content of J. mandshurica substrate treated with the mixed fungal agent was lower than that treated with the two single fungal agents, but the DOC content of L. gmelinii and mixed substrate treated with mixed fungal agent did not show the same significance. The degradation modes of J. mandshurica substrate treated with the three kinds of agent were same. The degradation mode of L. gmelinii substrate treated with agent B was the same as that treated with agent C, and the mode of mixed substrate treated with agent A was the same as that treated with agent C. This study shows that the types of litter affect the release capacity of DOC. The mixed fugal agent made of two strains with synergistic effect has stronger ability to degrade litters than that made of single strain, so as to promote the release of DOC. At the same time, it is also affected by the composition of litter substrates. This study provides a scientific basis for forest litter decomposition and carbon management in Maoer Mountain area by comparing the dynamic changes of DOC and degradation modes of different types of litter under the treatment of degrading agents.