The invention discloses a composition for treating cow mastitis and a preparation method of the composition. The composition comprises pangolin, honeysuckle, cortex fraxini, dandelion, semiaquilegia,radix salviae miltiorrhizae, ligusticum wallichii, mangnolia officinalis, fructus forsythia, loofah sponge, herba violae, astragalus membranaceus, angelica sinensis, cowherb seed, liquorice, and rhizoma cyperi; water is added to soak the above materials, and the materials are decocted to prepare the composition. The composition has a wide source of materials, is low in cost, is convenient to use,is safe and effectively, has the effects of activating blood to promote menstruation, dissipating blood stasis, fighting bacteria, diminishing inflammation and dredging breast collaterals, is nonspecific antibacterial, and not only has the advantages of directly inhibiting and killing the bacteria, but also has the effects of enhancing resistance and immunity of the body.