The invention discloses a compound oral liquid for treating children diarrhea and a preparation method thereof. The compound oral liquid for treating the children diarrhea comprises the following components of Nutrilite Double powder, dideoxyinosine, gastrodia elata polypeptide, disaccharidase, ribavirin, racecadotril, bismuth pectin, hydrotalcite, dry yeast, probiotics, potassium chloride, sodium chloride, sodium lactate, calcium gluconate, corrigent, emulsifying agent, buffer liquid, and antioxidant. The compound oral liquid for treating the children diarrhea has the advantages that the environment of children gastrointestinal tracts is improved, the effective microbial community is increased, the digestion and adsorbing of gastrointestinal tract are promoted, the water-electrolyte metabolic disorder is prevented, and the body immunity is improved; the cost is low, the toxic or side effect is little, the compound oral liquid can be used for a long time, and the children diarrhea can be prevented and thoroughly cured after long-time administration.