Objective The incidence of stroke in China has been growing year by year and has become the first cause of death exceeding cancer and heart disease. However, non-standard thrombolytic drug dose and therapeutic time window have seriously affected the treating effect of acute ischemic stroke. This study aims to explore the effect of intravenous alteplase with standard dose and reperfusion injury of ischemic brain tissue and prognosis of patients receiving thrombolytic therapy within therapeutic time window. Methods Clinical data of 86 patients with acute ischemic stroke receiving thrombolytic therapy with alteplase were retrospectively analyzed. Efficacy at 24 h and 3 months after thrombolysis was evaluated according to the multi-modal MRI, and the U.S. National Institutes of Health Stroke Scale (NHISS) and modified Rankin Scale (mRS) were used to identify the extent of neurological function improvement and prognosis of patients. Results Among 86 patients, 56 cases were anterior circulation ischemia, and 30 cases were posterior circulation ischemia. At 24 h after thrombolysis, 62 cases with favorable neurological function outcome accounted for 72.09%, and 24 cases with poor outcome accounted for 27.91%. The NHISS scores before and after thrombolysis were statistically different ( P = 0.023). Based on multi⁃modal MRI of 42 cases at 24 h after thrombolysis, there were 18 cases with complete vascular recanalization (42.86%), 6 cases with partial recanalization (14.28%) and 18 cases with occlusion (42.86%). The difference before and after thrombolytic thearpy was statistically significant ( P = 0.073). In the follow-up of 3 months, 78 patients with favorable function outcome accounted for 90.70%, and 8 cases with poor outcome accounted for 9.30%, which were significantly different from that before thrombolysis ( P = 0.008). Conclusion Cerebral vascular recanalization and reperfusion of brain tissue are reliable indicators of clinical efficacy for intravenous thrombolysis with alteplase.