Abstract：This paper introduces Professor CAO Rui's clinical experience in the diagnosis and treatment of chronic cough. Professor CAO Rui believes that the basic pathogenesis of chronic cough is lung failing to diffuse and purify，and ascending counterflow of lung qi. Therefore，the basic treatment principles are to purify the lung and direct counterflow downward，and to dissolve phlegm and relieve cough. At the same time，attention should be paid to regulating the qi mechanism，consolidating the exterior and regulating the ying level，and treating by stages. There is a difference between diffusing lung qi and lowering lung qi in clinical regulation of lung qi. The focus of regulating the qi mechanism in the whole body is on the liver ascending and stomach descending. In short， regulating qi mechanism should combine diffusing and governing descent，and governing descent weight more than diffusing. Treating by stages emphasizes the early stage of scattering wind and dissolving rheum，and the later stage of boosting qi and nourishing yin.