The main functions of the bile drainage bag include recording the drainage flow of bile, observing the character of the drainage bile, and temporarily storing bile. 1. Record the flow of bile: generally record the flow of bile within 24 hours, through the record of bile drainage, it is convenient to observe the electrolyte condition of the patient, and observe whether the amount of bile discharged by the patient is within the normal range. 2. Observe the character of the drained bile: It is convenient to observe the color of the bile through the drainage bag, such as observing whether there is blood or pus to judge the patient’s condition. 3. Temporary storage of bile: The bile drainage bag can temporarily store bile, avoiding bile stasis, maintaining smooth bile discharge, lowering the pressure in the bile ducts, preventing secondary infections and damage to liver tissues, and relieving the patient’s symptoms. It should be noted that when using drainage bags should be replaced regularly to keep the drainage smooth, keep the local skin dry and avoid infection.