This study aimed to find a quick and timely way to predict the individual variation of efficacy of opioid analgesic during the operation and postoperative analgesia in Chinese patients undergoing elective surgeries. Methods: female patients receiving elective surgery under general anesthesia were recruited into this study. At the time of routine intravenous anesthetic induction we observe the efficacy of opioid analgesic including analgesic effect, effects on Narcotrend index, sedative effect, effects on respiratory system, and aslo effects on cardiovascular system. Then we record the consumption of of opioid analgesic during the operation and postoperative analgesia. Also we record the side effect of the opioid analgesic.