Objective To study the effect of blood glucose fluctuations on the prognosis of thrombolytic therapy in patients with acute cerebral infarction. Methods A total of 83 consecutive patients with acute cerebral infarction admitted to the Department of Neurology,General Hospital of Beijing Military Command ( the Affiliated 81st Brain Hospital ) from January to November 2013 were enrolled retrospectively. They were divided into cerebral infarction with type 2 diabetes mellitus group (DMCI group,n=47) and cerebral infarction without type 2 diabetes mellitus group (NDMCI group,n=36) according to whether they had diabetes mellitus or not and the results of oral glucose tolerance test at day 7 after admission. Continuous glucose monitoring system ( CGMS) was used to monitor glucose for 72 hours at day 7 after admission. The mean blood glucose, standard deviation of blood glucose level, mean blood glucose fluctuation,and hemorrhagic transformation during the follow-up period,as well as vascular recanalization were observed and compared. At day 90,the modified Rankin scale (mRS) score was used to evaluate the prognosis of the patients. Results ( 1 ) Comparing the dynamic glucose parameters of the patients with acute cerebral infarction in both groups,the mean blood glucose,standard deviation of blood glucose level,mean blood glucose fluctuations at 24 hours in patients of the DMCI group were higher than those of the NDMCI group ( 8 . 3 ± 2 . 6 mmol/L vs. 5 . 8 ± 1 . 3 mmol/L,2. 1 ± 0. 4 mmol/L vs. 1. 6 ± 0. 6 mmol/L,4. 3 ± 0. 8 mmol/L vs. 3. 6 ± 0. 5 mmol/L). There were significant differences (t=31. 419, 15.537,and 15. 372,respectively;all P<0. 01). (2) Four patients (8.5%) in the DMCI group had hemorrhagic transformation during the follow-up period,17 cases (36. 2%) had good recanalization,and 15 cases (31.9%) had good prognosis (the mRS score < 2 at day 90);1 patient (2.8%) in the NDMCI group had hemorrhagic transformation,21 patients (58. 3%) had good recanalization,and 21 cases (58. 3%) had good prognosis. There was significant difference between the recanalization after thrombolysis and the prognosis in patients of both groups (P<0. 05). Conclusion The great fluctuations of blood glucose in acute cerebral infarction patients with type 2 diabetes mellitus may be an important factor of affecting its prognosis of thrombolytic therapy.