Advanced tumors (such as gastric cancer, colorectal cancer, ovarian cancer, etc.) are very likely to infiltrate the plasma membrane, form abdominal implantation and metastasis, and cause malignant ascites, which is clinically difficult to deal with and the efficacy is unsatisfactory, so doctors often feel helpless. Although some patients can undergo radical surgery and postoperative systemic chemotherapy, due to the existence of peritoneal-plasma barrier, very few chemotherapeutic drugs enter the peritoneal cavity during postoperative systemic chemotherapy and have limited effect on free cancer cells (FCC) in the peritoneal cavity, so the main reason for treatment failure is still intraperitoneal dissemination. In order to allow more chemotherapeutic agents to reach the lesion directly, medical colleagues have started to experiment with the technique of intraperitoneal thermal perfusion chemotherapy. Clinical studies in recent years have confirmed that this method is an effective way to treat progressive gastric, colorectal and ovarian cancers with ascites. It is to mix chemotherapeutic drugs with large volume perfusion solution and heat them, then inject them into the patient’s abdominal cavity with constant temperature in a continuous cycle and maintain them for a certain period of time. Through the synergistic effect of thermal chemotherapy and the flushing effect of large-capacity perfusion, it effectively kills and removes residual cancer cells and micro-metastases in the abdominal cavity, and prevents and treats peritoneal metastatic cancer. According to the existing studies, the main reasons why it can be effective are as follows: 1. Continuous circulating peritoneal thermal perfusion therapy can play a mechanical flushing effect on supraperitoneal implantation metastases and intraperitoneal cavity, and remove residual cancer cells and micro metastases in the peritoneal cavity. 2.The thermal effect of HIPEC has multiple effects on cancer cells, leading to microvascular embolization and tumor cell degeneration and necrosis at the tissue level; destroying the self-stabilization mechanism of cells at the cellular level, activating lysosomes, destroying cytoplasm and nucleus and inducing apoptosis; denaturing cancer cell membrane proteins at the molecular level, interfering with protein, DNA and RNA synthesis. The synergistic effect of heat and chemotherapeutic drugs is obviously enhanced at 42°C. The heat effect can enhance the permeability of anticancer drugs and increase the penetration depth of drugs from 1~2mm to 5mm. Meanwhile, since the drugs are mainly absorbed through the portal vein system, it also has a stronger effect on killing the cancer clots and cancer cells metastasized into the liver from the portal vein. 4. Heat therapy can also enhance the immune function of the body. Tumor cells can synthesize heat shock protein after heating, which stimulates the body’s immune system and generates specific immune response. Regardless of the primary or metastatic foci, heat therapy can produce immune activation effect, which can lead to the extinction of local or distant lesions.