Objective To investigate the functional outcome in patients with mild ischemic stroke and to identify its risk factors for poor outcome.Methods The patients with mild ischemic stroke treated within 72 hours after onset were enrolled prospectively.According to modified Rankin Scale (mRS) scores at day 90 after onset,the patients were randomly divided into either a poor outcome group (mRS score ＞2) or a good outcome group (mRS scores 0-2).Univariate analysis and multivariate logistic regression analysis were used to compare and analyze the demographic data,vascular risk factors,clinical data,laboratory data,imaging data,and follow-up data.The risk factors for poor outcome in patients with mild ischemic stroke were identified.Results A total of 253 patients with mild ischemic stroke were enrolled,and 71 of them (28.1％) had poor outcome.Univariate regression analysis showed that the patients' proportions of age (t =2.037,P =0.043),baseline National Institutes of Health Stroke Scale (NIHSS) score (U =4 610.000,P =0.000),baseline mRS score (U =5 723.000,P =0.000),as well as previous history of ischemic stroke (x2 =4.950,P =0.026),severe symptomatic artery stenosis or occlusion (x2 =49.037,P =0.000),large artery atherosclerotic stroke (x2 =34.359,P =0.000),early neurologic deterioration (x2 =45.804,P =0.000),complicated by pneumonia (x2 =12.121,P =0.000) and recurrent ischemic stroke (x2 =14.305,P =0.000) of the poor outcome group were significantly higher than those of the good outcome group.Multivariate logistic regression analysis showed that advanced age (odds ratio [OR] 1.049,95％ confidence interval [CI] 1.012-1.086; P =0.008),higher baseline mRS score (OR,2.130,95％ CI 1.212-3.743;P=0.009),higher baseline NIHSS score (OR 1.532,95％ CI 1.064-2.206; P=0.022),severe symptomatic large artery stenosis or occlusion (OR 7.569,95％ CI 3.497-16.380; P=0.000),early neurological deterioration (OR 7.369,95％ CI 2.648-20.510; P =0.000) and recurrent ischemic stroke (OR 10.450,95％ CI 3.071-35.564; P =0.000) were the independent risk factors for poor outcome.Conclusions More than one fourth of the patients with mild ischemic stroke had poor outcome.Advanced age,higher baseline mRS score,higher baseline NIHSS score,severe symptomatic large artery stenosis or occlusion,early neurological deterioration,and recurrent ischemic stroke were the independent risk factors for poor outcome.