It was shown that the cerebral ischemia-reperfusion produced free radicals are the main factor that causes irreversible cerebral injury. The mechanism of Naoxin Sutong (NXST) treated acute cerebral infarction was elucidated. It is compared with Ligustrazine (LT), which has been proved to be an effective drug for cerebral infarction. The curative effect and the changes of serum malondialdehyde (MDA) levels, blood rheology, blood lipid, etc. of 41 patients with acute cerebral infarction within 3 days, who were confirmed by CT. The therapeutic result showed that after 4 weeks of treatment the points of progress for central nervous system deficit scoring of NXST and LT group were 10.67 +/- 5.02 and 6.85 +/- 4.49 respectively. The difference between these two groups was significant. MDA levels of the patients and the healthy subjects were 6.46 +/- 1.70 and 3.87 +/- 0.67 nmol/ml respectively, the difference was also significant (P < 0.01). After 2 weeks of treatment, MDA content of NXST was less than before (P < 0.05). However the level of LT group did not reduce, while after 3 weeks of treatment, MDA content of NXST group was 4.34 nmol/ml. It was much less than that of LT group and approached that of healthy subjects. Results also showed that blood rheology improved, blood lipid reduced after NXST treatment. All these indicated that the effect of NXST in treating acute cerebral infarction was good, and the mechanism as that NXST could scavenge free radicals, ameliorate cerebral ischemia-reperfusion injury, improve blood rheology and reduce blood lipid.