Objective To study the relation between the levels of protein C(PC),protein S(PS),antithrombin Ⅲ(AT-Ⅲ)with cerebral infarction.Methods 126 patients with cerebral infarction were divided into the groups according to the age,onset time and infarction area and contemporaneous 30 individuals with healthy physical examination were selected as the control group.The levels of PC,PS and AT-Ⅲ were detected.The relation between the change of these indicator levels with the age,onset time and infarction area was analyzed Results The levels of AT-Ⅲ,PC and PS in the acute stage youth group were lower than those in the acute stage middle age and elderly group with statistical differences between them (P <0.05).The level of the AT-Ⅲ,PC and PS in the acute stage group were lower than those in the recovery stage group and the control group,difference had statistical significance(P <0.05).The levels of AT-Ⅲ and PS in the recovery stage group were lower than those in the control group with statistical difference (P <0.05),but the level of PC had no statistical difference between the recovery stage group and the control group.The further study found that the level of AT-Ⅲ,PC and PS in the small infarction group,middle infarction group and large infarction group showed the gradually decreasing trend,the differences had statistical significance (P <0.05).Conclusion The decrease of AT-Ⅲ, PC and PS levels is the importan factor of cerebral infarction occurrence and is closely correlated with cerebral infarction ocurrence especially in the patients less than 45 years old.Observing the change of PC,PS and AT-Ⅲ levels has the important significance for judging the cerebral infarction progression.