Abstract: Compost products could be used as organic fertilizer or soil conditioner, and could play an important role in the protection of groundwater as microbial carrier in the vadose zone. The present study is aimed at exploring the mechanism of microbial agents for improving the composting process. Metaproteomics was employed to investigate the influence of microbial agents on the structure of functional microbial communities and carbohydrate metabolism in food waste composting. The results showed that the relative abundance of order Pseudomonadales and class Eurotiomycetes increased by 12.5% and 22.0% respectively, and they replaced Bacilli and Saccharomycetes as dominant microbial communities with respect to total protein abundance and carbohydrate metabolic activity in the treatment group. The microbial agent was composed of Aspergillus and order Bacillales, and the Aspergillus was the main player in lignocellulose decomposition in food waste composting. This suggested that the Aspergillus became the dominant communities due to its roles in lignocellulose degradation, whereas the order Bacillales could not become the dominant bacteria because of competition interaction between microbial agent and indigenous microorganisms. The organic acids produced by decomposition of easily degradable organic matter in food waste could result in an acidic environment. In the control group, the Bacilli and Saccharomycetes were able to adapt to the acidic conditions and became the dominant communities. Whereas in the treatment group, the indigenous Pseudomonadales and Eurotiomycetes had high carbohydrate metabolic activity and various metabolic pathways of organic acids, so they replaced Bacilli and Saccharomycetes as dominant communities. The effectiveness of exogenous microbial agents and indigenous microorganisms depends on their adaptation to the metabolism in the composting process.