Professor WEI Pin-kang believes that, as a complication of gastric cancer, malignant ascites and gastric cancer have the same pathogenesis: water and dampness retention is the external performance and phlegm resistance is the inner essence. Hence therapy of resolving phlegm and promoting diuresis is suggested for the fundamental treatment of gastric ascites. Using the method of the combination of internal and external treatment, this therapy includes resolving phlegm and draining water medicine both to dispel pathogen and to improve symptoms. Xiaotan LishuiDecoction based on this therapy is composed of Arisacma Cum Bile, processed Pinelliae Rhizome, Cremastrae Pseudobulbus Pleiones Pseudobulbus, old pericarp of bottle gourd, Polyporus, Natriee Sulfas, Phytolaccae Radix and Poria.