In this article， Professor Liu Sheng’s experience in treating postoperative lymphedema by focusing on qi， blood and water in breast cancer patients has been introduced and his main idea comes from the theory of “unsmooth blood circulation resulting in water retention”. Pro. Liu believes that “qi-transformation and qi-blood circulation is everywhere inside the body”. Therefore， the dysfunction of qi-transformation and water metabolism is the key to the occurrence of postoperative lymphedema， and the core pathogenesis is “unsmooth blood circulation resulting in water retention”. In terms of treatment， Professor Liu advocates a balance between supporting the vital qi and dispelling the pathogenic qi. Specifically， the methods of tonifying the kidneys， strengthening the spleen， benefiting qi and nourishing the blood are adopted to strengthen the root， while the methods of removing blood stasis with drastic medicinals and expelling blood stasis， inducing diuresis to remove edema are used to dispel the pathogenic factors. One proven case is presented for exemplification.