Objective To evaluate the effect and safety of different doses of alteplase on acute ischemic stroke (AIS) patients less than 70 years old. Methods From October 2012 to June 2016， 184 AIS patients less than 70 years were randomly divided into standard dose group (n=93) and low dose group (n=91). 0.9 mg/kg and 0.6 mg/kg alteplase were given for intravenous thrombolysis respectively. The differences in the mortality rate and modified Rankin Scale (mRS) were compared between two groups at 90 days after treatment. The incidence of symptomatic intracranial hemorrhage (SICH) and other adverse events were evaluated meantime. Results Totals of 92 cases and 91 cases in two groups completed the study respectively. The mortality rates of patients in two groups were 10.87% and 8.79% within 90 days after onset of the disease respectively. There was no significant difference between two groups (P＞ 0.05). The death or neurological deterioration rate in 72 h after onset of the disease in two groups was 14.13% and 12.09% (P＞ 0.05). There was no significant difference in mRS distribution between two groups (P＞ 0.05). The incidence of SICH in two groups was 7.53% and 5.49% respectively (P＞ 0.05). The overall incidence of adverse events in two groups was 19.35% and 18.68% (P＞ 0.05). Conclusions The thrombolytic effect of low-dose alteplase on non-elderly acute ischemic stroke patients is well. The prognosis and risk of hemorrhagic transformation are comparable to the standard dose.