In the clinical practice of long-term treatment of chronic obstructive pulmonary disease, Professor Xue Hanrong attaches great importance to the theory of ' kidney is the root of phlegm ', and believes that kidney deficiency is an important internal cause of phlegm turbidity. When distinguishing the physiological and pathological relationship between lung, spleen and kidney, he is good at treating chronic obstructive pulmonary disease with the method of regulating kidney, so as to achieve the purpose of ' no need to reduce phlegm and phlegm self-lowering '.