Objective To observe the Effect of combined general anesthesia with Small-dose Ketamine on postoperative pain. Methods: Fourty patients aged 29～83 yr (ASAⅠ～Ⅲ)scheduled for major abdominal surgery were randomly assigned to receive intraoperative low-dose ketamine(bolus dose of 0.5mg/Kg followed by continuous infusion of 5 μg•kg-1•min-1) or an equal volume of saline during remifentanil/sevoflurane anesthesia.Then anesthesia was induced with midazolam 0.03mg/Kg, fentanyl 2μg/Kg, vecuronium 0.1mg/Kg, propofol 1-2mg/Kg. The index of hemodynamics and Bispectral index of the electroencephalogram were recorded at following time points: before induction、after induction、orotracheal intubation、 piece 、skin closure and extubation; The time point of emergence from anesthesia and extubation; Pain scores、sedation scores and postoperative tramodal consumption were recored. Awakening time and extubation time were recorded as well. Results: KG group VRS in 15 minutes after extubation were lower than CG group（P <0.01） ;Ramsay sedation score were higher than CG group（P <0.01）; Patients required tramadol earlier than in KG group for the first time（P <0.05）; Tramadol comsumption in PACU were much more than KG group （P <0.01）. Conclusion: Intraoperative low-dose ketamine could lighten postoperative pain and sedation score 、decrease tramodal consumption. These data suggest that small-dose ketamine could prevent clinically relevant concentrations of remifentanil-induced postoperative hyperalgesia; Intraoperative low-dose ketamine had no effect on awakening time and extubation time, which suggest that it could be safety compounded in general anesthesia.