Objective To investigate the relationship between plasma CX3CL1 level and severityand prognosis of patients with acute cerebral infarction. Methods The clinical data and plasma of 139 acute cerebral infarction patients (case group) and 82 healthy controls (control group) were collected. Plasma CX3CL1 levels were determined by ELISA. Patients in case group were tested by NIHSS within 24 h after admission，and then tested by mRS after 3 months. Level of plasma CX3XL1 was compared between subgroups divided accord-ing to NIHSS score and mRS score in case group. Results Compared with control group，the level of plasmaCX3CL1 in case group were significantly lower (P=0.009). Logistic analysis showed that plasma CX3CL1 levelwas associated with the occurrence of acute cerebral infarction (OR=0.387，P=0.020). And there was a signifi-cant negative correlation between CRP and plasma CX3CL1 level (r=-0.232，P=0.003). There was a significant negative correlation between the plasma CX3CL1 level and the NIHSS score within 24 h after admission (r=-0.179，P=0.034). Compared with good outcome patients (mRS ＞2)，the poor outcome patients (mRS ≤2) had significant higher leukocyte count and CRP，and lower plasma CX3CL1 level (all P ＜0.05). And there was a significant negative correlation between the plasma CX3CL1 level and the mRS score after 3 months of acute ce-rebral infarction (r=-0.263，P=0.002). Logistic analysis showed that plasma CX3CL1 level was associated withthe prognosis of the patients (OR=0.087，P=0.004). Conclusions The plasma CX3CL1 level of acute cerebral infarction patients was lower. And the plasma CX3CL1 level was significantly associated with the severity andprognosis of acute cerebral infarction patients.