Multiple myeloma is a malignant hematologic disease prone to occur in the elderly. Patients with poor immune function after the onset of the disease are prone to various infections, such as lung infections or pneumonia, urinary tract infections, herpes zoster and other infections, and also gastrointestinal infections that cause diarrhea. Patients with diarrhea should be tested for stool routine to determine whether it is infectious diarrhea, and they need to ask about the history of medication to find the cause of diarrhea before deciding on a treatment plan. However, it is correct to give drugs such as Flavopiridol and Simethicone to control diarrhea first. Then adjust the treatment accordingly based on the medication history and laboratory results. If the diarrhea is infectious, anti-infective treatment should be intensified. If there is no evidence of infection and the reaction is due to the use of Vanco, strong anti-diarrheal drugs such as Emmenagogue should be added under the guidance of the doctor in charge (the treatment should not be too long).