Gastric cancer remains one of the most prevalent tumors worldwide and peritoneal metastasis is responsible for approximately 60% of death in advanced gastric cancer patients. However, the underlying mechanism of peritoneal metastasis is poorly understood. We have established organoids derived from malignant ascites (MA) of gastric cancer patients and noticed that MA supernatant could strongly increase the colony formation of organoids. Thus, we realized the interaction between exfoliated cancer cells (ECCs) and liquid tumor microenvironment contributes to peritoneal metastasis. Further, we designed a medium component control test which proved that exosomes derived from MA could not enhance the growth of organoids. Using Immunofluorescence and confocal imaging as well as dual-luciferase reporter assay, our data showedWNTsignaling pathway was upregulated by high concentrations ofWNTligands (wnt3a and wnt5a), which was verified by ELISA. Besides, suppressingWNTsignaling pathway diminished the growth promoting function of MA supernatant. This result implicatedWNTsignaling pathway as a potential therapeutic target for peritoneal metastasis of gastric cancer.