Abstract：The experience of Professor CHENG Jiazheng in treating children with diarrhea by using modified Qiwei Baizhu powder was summarized，Professor CHENG Jiazheng holds that the lung，the spleen，and the kidney of children are often insufficient；either external contraction or internal damage can easily lead to diarrhea，Since the key of pathogenesis is the spleen deficiency and excessive dampness，the treatment should focus on fortifying the spleen and invigorating the stomach as well as resolving dampness to check diarrhea， which are assisted by methods of tonifying qi and nourishing yin， dispersing cold and removing stagnation，as well as warming yang and astringing the intestines，The clinical application of modified Qiwei Baizhu powder has a good curative effect，Typical medical records are attached for verification.