Objective To study the age difference of remifentanil in pharmacokinetics. Methods ASA class Ⅰ or Ⅱ patient,s undergoing selective operation under general anestesia were assigned into group A (65 to 82 years old) and group B(18 to 64 years old) with 60 cases each. Remifentanil 4 μg/kg was infused during induction. Arterial blood samples 1 ml were taken at 1,2,3,5,7,10,15,20,25,30,45,60 min after injection and the concentrations of remifentanil were detected using liquid-liquid extraction and capillary GC-MS-SIM. Results The values of elimination half-tirne(t_(1/2β)), volume distribution(Vd) and clearance(CL) were significantly higher in group A than those in group B[t_(1/2β), (18. 1±9. 2) min vs. (9. 4±4. 6) min, Vd, (60.7±18.2) L vs. (45.3±10.6)L, CL, (2.1±0.3) L/min vs. (3.8±0.4) L/min](P<0.05). Conclusion The t_(1/2β),Vd and CL are significantly higher in the elderly than those in the younger.