Background　Propofol，an intravenous anesthetic is widely used in anesthesia induction， maintenance and sedation in intensive care patients. However， the injection pain experienced during intravenous administration of propofol remains a problem.　Objective　To investigate the effects of opioids on prevention of propofol injection pain.　Content　Summary the effects of opioids on prevention of propofol injection pain and its mechanism.　Trend　Searching a suitable method for the prevention of propofol injection pain.