Primary bronchial lung cancer, short for lung cancer, refers to the alveolar carcinoma originated at bronchial mucosa. Based on long-term clinical experience, Professor Zheng Weida summarized that the cancer was mostly caused by the weakness of inner healthy qi and inner accumulation of evil toxin. The pathogenesis of the cancer is the following: stasis evil invading lung; phlegm-dampness accumulation and the weakness of inner healthy qi. The principles of treatment should be resolving stasis and removing toxin, nourishing yin and clearing heat, invigorating spleen and resolving phlegm as well as replenishing qi and tonifying deficiency. Formulated by Zedoray Rhizome, Edible Tulip, Nux Vomica, Cow-Bezoar, Milkvetch Root, Radix Angelicae Sinensis and other five materia medicas, Cidan Capsule has the effect of resolving stasis and removing toxin, alleviating edema and dissipating mass, replenishing qi and tonifying middle. Professor Zheng made great improvement in treating primary lung cancer by Cidan Capsule. This passage summarized his classical cases in treating the cancer and clinical experience of using Cidan Capsule.