Malignant Peritoneal Effusion (MPE) in gastrointestinal tumors can affect the prognosis of patients with advanced cancer. It is associated with multiple factors such as abnormal angiogenesis, a damaged lymphatic system, and an inflammatory response. After the onset of the disease, tumor cells invade the peritoneum, and changes in the peritoneal microenvironment can increase vascular permeability. Additionally, factors such as the high number of neovascularizations in patients with malignant tumors, lymphatic circulation disorders, and intensified inflammatory responses in the body create a vicious cycle, leading to increased production of ascites. Clinically, imaging techniques, cytological techniques, and biomarker detection techniques are commonly used to diagnose MPE, and treatment options and prognostic factors are explored through clinical practice. This study analyzes the diagnosis and treatment methods of MPE from multiple perspectives, providing a basis for summarizing new diagnosis and treatment methods for MPE in the later stage.