The purpose of this study was to elucidate the effect of Oldenlandiae herba and Houttuyniae cordata on calf diarrhea in farms. We examined the antibacterial and antiviral effect of Oldenlandiae herba and Houttuyniae cordata extracts in vitro. And we divided diarrheal calves into three roups in farm; Oldenlandiae herba administration group(10 calves), Oldenlandiae herba and Houttuyniae cordata administration group(10 calves) and control group(7 calves). We estimated the therapeutic effect of the calf diarrhea by using clinical signs, CBC, AST, BUN, creatinine, and measurement of lymphocyte distribution in whole blood. Oldenlandiae herba and Houttuyniae cordata extracts by ethanol(98%) had antibacterial and antiviral effect. In the condition of diarrhea, the fecal condition of Oldenlandiae herba and Houttuyniae cordata group was relieved more than that of others group during experimental period. PCV and fibrinogen concentrations were high in control group. AST and BUN were within normal range in all groups. Administration of Oldenlandiae herba and Houttuyniae cordata was not toxic to the liver and kidney. And Oldenlandiae herba and Houttuyniae cordata extracts also affected the lymphocytes distribution in blood. From these results, we suggested that administration of Oldenlandiae herba and Houttuyniae cordata should be effective on the dairy calf diarrhea in farms.