Objective To study the mechanism of lidocaine injection in the alleviation of pains of propofol injection. Methods 430 patients, who underwent elective gastrointestinal endoscopy under general anesthesia , were randomly assigned into 3 groups: group A received 2 mL NS intravenous injection on the right dorsal hand;group B received 40 mg Lidocaine intravenous injection on the right dorsal hand and group C received 40 mg lidocaine intravenous injection on the left dorsal hand. All groups received 2 mg/kg Propofol intravenous injectionon the right dorsal hand at the rate of 20 mL/min. The injection pains were evaluated while the dosage reached 1/4 of the total (2 mg/kg). The left dosage of Propofol and 50 μg Fentanil were pumped after evaluation. Propofol dosage was added when needed. Mean arterial pressure (MAP) and heart rate (HR ) were recorded before Propofol injection and 1, 3, 5 minutes after Propofol injection. Results VRS comparisons: Tthe rate of pain incidence of group B was significantly lower than those of group A and C. MAP were declined dramatically at the time points of 1 minute, 3 minutes and 5 minutes after propofol injection, as compared to before propofol injection. The HR was declined dramatically 5 minutes after propofol injection. Conclusion Intravenous Lidocaine of 40 mgcould reduce Propofol-induced injection pain of the same vein. Local effect of Lidocaine but not its systemic function may play an important role in reducing Propofol-induced injection pain.