Objective: To observe the relationships between serum matrix metalloproteinase-9 (MMP-9) level and cognitive dysfunction after cerebral infarction of patients with acute cerebral infarction. Methods: Initial cerebral infarction patients were divided into cognitive dysfunction group (≤26) and non cognitive dysfunction group (<26) according to MoCA score. Healthy checkup at the same term were taken as healthy control group. ELISA was used to detect the serum MMP-9 level of 124 subjects. Results: The serum MMP-9 level of patients in cognitive dysfunction group was obviously higher than non cognitive dysfunction group and healthy control group (P<0.05). Logistic regression showed that MMP-9 and age were independent risk factors for cognitive dysfunction after cerebral infarction. Conclusions: Increasing of serum MMP-9 level in patients with acute cerebral infarction maybe related to cognitive dysfunction after cerebral infarction.