Objective: The purpose of this study was to better understand the epidemiological features and outcomes of emergency medical service(EMS)-assessed out-of-hospital cardiac arrests(OHCAs) in Kunming,Yunnan,China. Methods: In this prospective study,datas were collected according to the Utstein style on all cases of OHCAs from January 2010 to December 2014 in urban areas covered by Kunming EMS system.The outcomes were analysed at four time points of survival: no return of spontaneous circulation (no-ROSC),return of spontaneous circulation (ROSC),survival to hospital admission, and survival to hospital discharge.The adjusted odds ratios(ORs) and 95% confidence intervals(CIs) for survival were calculated and adjusted for potential risk factors using stratified multivariable logistic regression analysis. Results: There were 3387 EMS-assessed OHCAs with cardiac aetiology from 2010 to 2014. The incidence of EMS-assessed OHCA with cardiac aetiology was 20.7 per 100,000 inhabitants per year. Of the 3387 EMS-assessed OHCAs with cardiac aetiology,the rates of ROSC,survival to admission and survival to discharge were 12.4%,3.5% and 0.9% respectively. There were only 73(2.2%)patients with initial rhythm of ventricular fibrillation(VF) or pulseless ventricular tachycardia(VT) observed in the EMS-assessed OHCAs with cardiac aetiology.There was no statistical difference among the five years in outcomes of OHCAs with cardiac aetiology.Younger age, bystander CPR,witnessed by EMS, OHCA with initial rhythm of VF/pulseless VT,shorter medication interval,and shorter response interval were associated with a higher rate of survival to discharge respectively. Conclusion: In the urban areas of Kunming covered by EMS system, survival outcome of OHCA was unsatisfactory.Improvements are required in every link of the chain of survival.