OBJECTIVE To investigate the in vitro antibacterial effect of Asi-antidiarrheal capsule a Chinese herbal compound on hyperthyroid diarrhea.METHODS It was determined by drug dilution method in test tube to determine Asi-antidiarrhea capsule.The compound positive control drug was diphenoxylate co.We made in vitro antibacterial test with 8 kinds of bacteria respectively.RESULTS Asi-antidiarrhea capsule had powerfully bacteriostatic action on Shigella dysenteriae,Staphylococcus aureus and Streptococcus pneumoniae(MIC31.25 mg/L).But diphenoxylate co contrally was less effective on S.aureus,Str.pneumoniae,Str.pyogenes and Sh.dysenteriae(MIC 0.25 mg/L).CONCLUSIONS Asi-antidiarrhea capsule can be used to hyperthyroid diarrhea.Meanwhile,it has powerfully antibacterial effect.It provides evidence of pharmacodynamics for healing infectious diarrhea in the future.