【Abstract】Objective To study effects of dexmedetomidine combined with spinal-epidural anesthesia on conscious-sedation and anterograde amnesia. Methods By OAA/S Method, we investigated 200 examples of the patients who were pumped diffent doses of dexmedetomidine combined with spinal-epidural anesthesia in order to studing effects of dexmedetomidine on conscious-sedation and anterograde amnesia. In 24h after operation, we investigated anterograde amnesia of those..Results Compared with De0 group [the OAA/S,s scores of De0 group of conscious-sedation was（5.00±0.00）at T2, T3，T4，T5，T6，T7 and T8 point], there were statistically significant of the different dose of dexmedetomidine on the OAA/S,s scores of conscious-sedation at T2, T3，T4，T5，T6，T7 and T8 point [The OAA/S,s scores of De1 group of conscious-sedation was（3.15±0.37）at T2 point，（3.26±0.44）at T3 point，（2.70±0.66 ）at T4 point，（2.55±0.60 ）at T5 point，（2.40±0.60）at T2 point，（2.05±0.76 ）at T7 point，(2.02 ±0.73）at T8point；The OAA/S,s scores of De2 group of conscious-sedation was（3.10±0.64）at T2 point，（2.95±0.51）at T3 point，（2.35±0.67）at T4 point，（2.25±0.55）at T5 point，（2.10±0.45）at T6point，（1.60±0.50）at T7point，（1.65±0.49）at T8 point；The OAA/S,s scores of De3 group of conscious-sedation was （3.10±0.31）at T2 point，（2.65±0.49）at T3 point，（1.95±0.39） at T4 point，（1.90±0.45）at T5 point，（1.75±0.44）at T6 point，（1.20±0.62）at T7 point，（1.25±0.64） at T8 point．]and the degree of anterograde amnesia[there was not anterograde amnesia of the De0 group，but there were 4 cases on total amnesia，35 cases part amnesia，11 cases no amnesia in theDe1 group； there were 15 cases on total amnesia，29 cases part amnesia，6 cases no amnesia in the De2 group，but there were 29 cases on total amnesia，19 cases part amnesia，2 cases no amnesia in the De3 group，] among other groups（P<0.05）．Compared with De1 group, there were statistically significant of those both De2 and De3 groups too（P<0.05）．Compared with De2 group, the OAA/S,s scores of De3 group of conscious-sedation and the degree of anterograde amnesia had become lower （P<0.05）．Conclusion There were better conscious-sedation and anterograde amnesia of dexmedetomidine，and those had dose dependent．