The invention discloses a western medicine combined preparation for treating diarrhea. The western medicine combined preparation is prepared from raw materials in parts by weight as follows: 5-10 parts of berberine, 8-10 parts of cysteine, 5-8 parts of methionine, 0.05-0.2 parts of gliclazide, 0.05-0.1 parts of phenformin, 2-5 parts of L-carnitine, 10-20 parts of piperazine ferulate, 15-20 parts of hydrochlorothiazide, 2-5 parts of imodium, 2-5 parts of chitosan, 1-5 parts of cisapride, 1-2 parts of Nuanwei Shule tablets and 0.01-0.05 parts of vitamin B1. The western medicine combined preparation has a better treatment effect on diarrhea, and the effective rate reaches 98%. Multiple raw materials are compounded to play a role of synergism, so that the preparation can realize effects of invigorating the spleen and stomach, stopping diarrhea and strengthening the intestines; besides, the western medicine combined preparation for treating diarrhea has the advantages of simple preparation method, low treatment cost, short treatment course, little toxic and side effects and little adverse reaction.