Background and Purpose: Emergency medical services (EMSs) is critical for the early treatment of ischemic stroke patients, yet data regarding EMSs utilization and its association with timely treatment are still limited in China. Methods: We examined the data from Chinese Stroke Center Alliance (CSCA) recording consecutive ischemic stroke patients from 2015 June to 2017 November. The absolute standardized difference was used for covariates balance assessments. We used multivariable logistic models to identify factors associated with EMSs usage and to evaluate the effect of EMSs on timely treatment. Results: Of the 326,534 analyzed ischemic patients, only 42,293 (13.0%) were transported by EMSs. Multivariable-adjusted results indicated that younger age, less education, non-urban employ medial insurance, lower income level, less stroke severity, smoking, history of stroke/transient ischemic attack, carotid stenosis, hypertension, diabetes and peripheral vascular disease were associated with decreased risk of EMSs usage. However, coronary heart disease or myocardial infarction, atrial fibrillation and heart failure were associated with increased risk of EMSs usage. Compared to self-transportation, EMS-transported patients were associated with significantly shorter onset-to-door time (Median (IQR): 210 (105-586) vs. 1020 (290-2250) minutes, P<0.0001), higher chance of arrival at hospitals within 2 hours (32.0% vs 9.4%, OR=3.77, 95% CI: 3.53-4.02) or within 3.5 hours (50.1% vs 19.0%, OR=3.60, 95% CI, 3.35-3.86) after symptom onset, and treated with IV tPA (13.8% vs 3.6%, OR=3.06, 95% CI:2.75-3.41). Conclusions: EMSs utilization is far from optimal among Chinse ischemic stroke patients. Nevertheless, use of EMSs transportation is associated with substantial reductions in prehospital delay and improved chance of timely treatment. Therefore, community education efforts are needed to improve EMSs activation.