Opioids are usually applied in controlling pain of patients who suffers from cancer. Besides, opioids are also used in patients with chronic pain and critical ill patients. Opioids may endanger health of human and cause many severe complications if the dosage or duration is not appropriate. Therefore, we must be alert in patients who need to use opioids. The article introduces the complications of opioids and ways to handle these to early prevent and handle these in critical ill patients. At the same time, we can enhance the safety of patients and quality of care.