This study selected high-yield carvacrol-type oregano essential oil distillation residues obtained from previous screening and compared them with different addition levels against a control group. The objective of this study was to investigate the impact of oregano essential oil distillation residues on the microbial composition during alfalfa silage fermentation by analysing the metaproteomics data obtained during the fermentation process. This research provides a theoretical foundation for the eco-friendly utilisation of essential oil distillation residues from aromatic plants.