Objective: To evaluate the protective effects of tetramethylpyrazine on acute cerebral ischemia/reperfusion injury after cardiopulmonary resuscitation in patients with organophosphorus pesticide poisoning. Methods: Consecutive thirtytwo patients were randomly divided into treatment group and control group.Eighteen patients in the treatment group were treated with tetramethylpyrazine 240 mg+5% glucose 250 ml infused intravenously for l hour once a day for 57 days. The treatment in the control group was the same as that of the treatment group except tetramethylpyrazine infusion omitted. Results: The therapeutic effects in the treatment group were markedly effective in 12 cases, effective in 4 cases and ineffective in 2 cases, the total effective rate being 88.9%. The effects in the control group were 6, 4, 4 and 71.4% respectively. The differences were significant between the two groups (P<0.05). In the treatment group, superoxide dismutase (SOD) was increased from (94.55±13.04)kNU/L before treatment to (102.46±15.22)kNU/L after treatment, lipid peroxide (LPO) was decreased from (6.88±1.32)μmol/L to (4.97±1.04)μmol/L, thromboxin B 2 (TXB 2) was decreased from (211.45±20.47)ng/L to (129.31±14.66)ng/L(all P<0.01). The plasma SOD, LPO and TXB 2 levels were improved in the two groups after treatment and the improvement was more superior to that of the control group. Conclusion: Tetramethylpyrazine has the effect of restraining lipid peroxidation, increasing the activity of SOD, inhibiting the activation of blood platelets and has the protective effect on acute cerebral ischemia/reperfusion injury after cardiopulmonary resuscitation in patients with organophosphorus pesticide poisoning. If it is used earlier, the successful therapeutic rate of cerebral resuscitation can be increased.