This experiment was conducted to investigate the effect of fermentation of a self-made compound traditional Chinese medicine (TCM) by Pleurotus ostreatus HXS-M1 on its main active components and antibacterial activities. Pleurotus ostreatus HXS-M1, a food-medicine homologous fungus, was used to ferment the compound TCM. The contents of active components of the compound TCM and the diameters of inhibition zones before and after fermentation were determined using ultraviolet–visible spectrophotometry and the Oxford cup method, respectively. The results showed that the contents of total polysaccharides, total alkaloids, total flavonoids, and total saponins in the compound TCM before and after fermentation had extremely significant differences (P<0.01). After fermentation, the contents of total polysaccharides and total alkaloids increased by 350.63% and 95.65%, respectively, while the contents of total flavonoids and total saponins decreased by 79.63% and 84.08%, respectively, compared with those in the non-fermented compound TCM. The diameters of the inhibition zones against Escherichia coli, Salmonella, and Staphylococcus aureus increased by 4.54 mm, 4.08 mm, and 5.33 mm, respectively, compared with those for the non-fermented compound TCM, and these differences were extremely significant (P<0.01). In conclusion, compound TCM fermented by Pleurotus ostreatus HXS-M1 can promote the release and biotransformation of active components, improve antibacterial activities, enhance the application effect, and provide a scientific basis for the development of high-efficiency TCM feed additives.