At present, pediatric postoperative analgesia has not been fully understood and controlled, particularly craniotomy surgery. On the one hand, professional evaluation of postoperative pain for young children is difficult; on the other hand, the particularity of craniotomy adds (such as consciousness obstacle, sleepiness, et al) disturbance to the pain assessment in children. Although opioids administration is regarded as the first-line analgesic for post-craniotomy pain management, it may be associated with delayed awakening, respiratory depression, hypercarbia and it may interfere with the neurologic examination. For the avoidance of side-effects of systemic opioids, local anesthetics administered around the incision have been performed clinically. However, some studies revealed that the analgesic effect of local anesthetics was unsatisfactory due to its short pain relief duration, steroid as adjuvant can enhance postoperative analgesia and prolong postoperative analgesia time. As is reported that postoperative pain of craniotomy is mainly caused by skin incision and reflection of muscles, preventing the liberation of inflammatory mediators around the incision seems to be more effective than simply blocking nerve conduction.However, there has not been reported about local application of triamcinolone acetonide on scalp infiltration. Thus, the investigators suppose that pre-emptive scalp infiltration with steroid (triamcinolone acetonide) plus local anesthetic (ropivacaine) could relieve postoperative pain after craniotomy in children.