This paper selects 7 typical ancient medical cases of misuse of Dachengqi Decoction,and analyzes the causes of its wrong treatment,including wrong identification of the cause of disease,failure to participate in the season,seeing the disease and treating the disease,shallow disease and deep medicine,being confined to the phenomenon,and being too early.In clinical practice,we must experience the meaning,observe the pathogenesis,judge the time and size up the situation,so as to hit the key point and remove the evil from the good.