Objective To study the effect of preemptive analgesina of morphine injected to subarachnoid space on postoperative epidural analgesia with morphine. Methods Sixty ASA Ⅰ-Ⅱ patients were randomly divided into two groups. All patinents received combination spinal-epidural anesthesia(CSEA). In experimenta group (n=30), 0 5% bupivacaine 2ml and morphine 0 5mg were injected into the subarachnoid space of the patients for CSEA, and morphine 2 8mg was used for postoperative epidural analgesia. In control group (n=30),0 5% bupivacaine 2ml was injected into the subarachnoid space of the patients for CSEA, and morphine 3 3mg was used for postoperative epidural analgesia. The numerical rating score (NRS) and Ramsay sedation scores were performed after operation. The postoperative analgesic duration and frequency of side effect were recorded. Rusult NRS was significantly less and postoperative analgesic duration was obviously longer in experimental group compared with control group. Ramsay sedation scores and the frequency of side effect significantly increased in the experimental group compared with the control group. But the shaking frequency in experimental group was significantly less than that in the control group. Conclusions Preemtive analgesia of morphine injected to subarachnoid space could improve postoperative epidural analgesia with morphine and increase analgesia time. But it had more side effects.