The invention discloses a pharmaceutical composition for treating dog dermatomycosis, and a preparation method thereof. The pharmaceutical composition comprises the components of matrine, bifonazole, dimethyl sulfoxide, glycerol and ethanol. Clinical observation experiment shows that the pharmaceutical composition has remarkable treatment effect for the dog skin diseases caused by various funguses, and has the whole treatment effect superior to other similar drugs. The pharmaceutical composition contains no hormone, has no side effect such as tolerance and the like which are common in other drugs, has the advantages of remarkable treatment effect, low toxic side effect, natural crude drugs, lower price and the like, and can be effectively used for treating dog dermatomycosis.