Fourty neurosurgical patients who were generally administered to sevofrane or echrane in operation gave been observed by means of computerized electroencephal monitor. Pa-tients were divided into sevofrane group and echrane group. Author found that there was a regular pattern of EEG and BEAM during anesthesia and operation,which dynamometer of slow frequency band increase with inspired agent concentration. When insired agent for general anesthesia arrived top. EEG showed burst suppression known by the name of IC value. The threshold of sevofrane's IC was evidently higher than echrane's. Occurrence of spike to sevofrane and echrane was 0/20 and 8/20 respectively.Conclusion promises sevofrane to be weaker than echrane in leading to seizure and be applicable to anaesthetise neurosurgical patient. IC value, can regard as one of indices to form a judgement of inspired anesthetic agent effection on central nervous system.