The navicular abdomen is a manifestation of the patient’s extremely malnourished state. The patient’s abdomen is clearly depressed after lying flat on the bed, like a boat, which is the feeling of the forehead against the back. It is usually seen in patients who are extremely thin and malnourished, with complete loss of subcutaneous fat, abdominal fat and fat in the abdominal cavity. The patient’s face is very thin, the limbs are also thin, the skin is flaccid, etc. For the treatment of severe malnutrition, if it is caused by simple malnutrition, enteral parenteral nutrition can be performed simultaneously. In the early stage of enteral and parenteral nutrition, the full amount should not be given, but the half amount should be given from the beginning. In case of tumor-induced cachexia, a systemic examination should be conducted at the same time of nutritional support to consider the next step of treatment, such as chemotherapy or tumor resection.