Objective To establish the emergency severity index scoring system for acute coronary syndrome patients with chest pain(ESISSACS), and to verify its application effect. Methods The data of 568 ACS patients with chest pain were analyzed retrospectively, then a Logistic regression model was established with the patients′general data as independent variables and their emergency severity index as dependent variable, the variables entering the regression model were considered as final items of ESISSACS,which were scored according to relative risk, the boundary values of ESISSACS were determined using the ROC curve, and its reliability and validity were evaluated. Finally, the established ESISSACS and Emergency Severity Index (ESI) were utilized to assess emergency severity of 515 ACS patients with chest pain, and the triage accuracy and time of triage were compared. Results ESISSACS included 13 triage items, the boundary value of ESIⅠ, Ⅱ, Ⅲ and ⅣⅤ was 11, 6, 4 and 3 respectively, and the corresponding area under ROC curve was 0.967、0.832、0.836、0.931 respectively, the Cronbach′s α coefficient of the scale was 0.675. Three common factors were extracted using exploratory factor analysis, with a cumulative contribution rate of variance of 63.152%. The triage accuracy rate of ESIⅠⅡ、Ⅲ、ⅣⅤ for ACS patients with chest pain using ESISSACS were significantly higher than those using ESI（P<0.05 for all）, while there was no significant difference in triage time consummation using ESISSACS (7.91±2.37) min and ESI (7.38±1.82) min（P>0.05）. 〖WTHZ〗Conclusion The established ESISSACS has good reliability and validity. Its clinical application increases the triage accuracy rate in ACS patients with chest pain, it could be used to assess the emergency severity for ACS patients.