The invention relates to a medicinal composition for treating skin diseases, which comprises the following active ingredients in part by weight: 45 to 55 parts of benzoic acid, 45 to 60 parts of boric acid, 20 to 30 parts of salicylic acid, 0.5 to 2.5 parts of furacilin, 10 to 20 parts of lightyellow sophora root and 2 to 10 parts of dehydrated alum. During the treatment of the skin diseases, theinvention has the advantages that (1) the medicinal composition is superactive and bactericidal, has quick response and high cure rate and can prevent relapse; (2) sterilization, itching relieving, pain relieving, hidroschesis and podobromidrosis removal are realized simultaneously; (3) dosage is little; and (4) the safety is high.