Granisetron hydrochloride is a highly selective 5-HT3 receptor antagonist, which has good preventive and therapeutic effects on nausea and vomiting caused by radiotherapy, chemotherapy and surgery. Radiotherapy, chemotherapy and surgery can cause the release of 5-HT from the intestinal chromaffin cells. 5-HT can activate the 5-HT3 receptor of the central or vagus nerve and cause vomiting reflex. The mechanism of controlling nausea and vomiting is to inhibit the occurrence of nausea and vomiting by antagonizing 5-HT3 receptors in central chemosensory area and peripheral vagus nerve endings. It has high selectivity and no side effects such as extrapyramidal reaction and excessive sedation.