Abstract：This article summarizes Professor JI Bing's clinical experience in treating lung cancer with Fuzheng Xiao'ai Decoction based on the theory of "yang governs qi-transformation，yin governs substance-formation". Professor JI Bing holds that the pathogenesis of lung cancer is rooted in insufficiency qi-transformation by yang，with excessive substance-formation by yin as the contributing condition. It involves yang qi deficiency of the lung， spleen， and kidney，leading to disordered qi transformation，internal generation of phlegm and blood stasis. Pathogenic toxins then take advantage of this condition to invade from outside or generate internally，retaining in the lung. After a prolonged course，these factors bind together and transform into cancerous toxins. Treatment should focus on supporting healthy qi and boosting qi， resolving phlegm and dispelling stasis， removing toxin and dissipating masses. In clinical practice， modified application of his self-formulated Fuzheng Xiao'ai Decoction based on syndrome differentiation has shown satisfactory efficacy.