Ｏｂｊｅｃｔｉｖｅ　To evaluate the effects of different doses of remifentanil on pain threshold in rats during withdrawal.　Methods　Forty adult male SD rats were randomly divided into 5 groups（n=8）， the model of long-term vascular access to mouse was established. The rats in remifentanil groups （R1， R2， R3 and R4 group） were injected with remifentanil 0.3， 0.6， 1.0 μg·kg-1·min-1， and 1.5 μg·kg-1·min-1 through jugular vein. The rats in saline group （N group） were injected with 0.1 ml·kg-1·min-1 normal saline through jugular vein. All rats were continuously exposed to remifentanil or saline for 4 h. The response to thermal noxious stimulation was determined before and after model establishment， 0.5， 1， 2， 24， 48 h after remifentanil withdrawal （treatment groups） and saline （control group）（T1-T7）.　Results　There is no significant difference in baseline threshold of heat stimulus after jugular vein catheterization in rats. The threshold of heat stimulus reached the minimum level at half an hour after remifentanil withdrawal. The threshold of heat stimulus decreased by 34.0%， 30.8%， 13.3% and 10.6% on T3 in R4（3.3±0.3） s， R3（3.6±0.5） s， R2（3.9±0.3） s and R1（4.2±0.9） s group， and decreased by 28.3%， 21.7%， 15.2% （P<0.05）， 8.7% than that in N group （4.6±0.4） s （P<0.05）. The threshold of heat stimulus decreased by 30.0%， 26.0%， 11.1%， 10.6% in R4（3.5±0.4） s， R3（3.7±0.4） s， R2（4.0±0.4） s and R1（4.2±0.8） s group on T4 than that on T2（P<0.05）. Compared with T2， the threshold of heat stimulus on T3［（3.3±0.3）， （3.6±0.5） s］， T4［（3.5±0.4）， （3.7±0.4） s］ and T5［（3.9±0.4）， （4.2±0.7） s］ significantly increased in R4 and R3 groups（P<0.05）. There exist no diffference in the others.　Conclusions　Different doses of remifentanil infusion can result in acute hyperalgesia higher dose， the greater the extent of pain threshold decline.