The present invention discloses a mastitis treatment anti-inflammation and swelling subsiding oral liquid and a preparation method thereof. The mastitis treatment anti-inflammation and swelling subsiding oral liquid is prepared from the following raw materials by weight: 15-20 parts of milkvetch root, 10-15 parts of cowherb seed, 20-30 parts of burdock leaf, 12-18 parts of weeping forsythia fruit, 5-10 parts of herba verbenae offcinalis, 10-15 parts of beautiful sweetgum fruit, 16-22 parts of loofah, 8-14 parts of semen trichosanthis, 12-18 parts of lysimachia fortunei, 15-20 parts of radix angelicae pubescentis, 20-25 parts of dandelion, 6-12 parts of lobelia chinensis, 10-15 parts of tangerine leaf, 12-18 parts of vernonia patula, 16-22 parts of bupleurum chinense, 5-10 parts of immature tangerine fruit, 18-24 parts of cushaw flower, and 10-15 parts of paniculate bolbostemma bulb. According to the present invention, the oral liquid is prepared by carrying out compatibility of a plurality of pure nature traditional Chinese medicines, various drugs are combined, effects of anti-inflammation, swelling subsiding, stagnation eliminating, boil treating, collateral dredging, stasis eliminating, heat clearing and lactogenesis are provided, the human body immune function can be improved, good treatment effects are provided for mastitis caused by a variety of causes, and the mastitis treatment anti-inflammation and swelling subsiding oral liquid has characteristics of quick effect, significant treatment effect, short treatment course, high cure rate, low recurrence rate, no toxic-side effect, no adverse reaction, safety and reliability.