Objective To study the comprehensive quality of pre-hospital care of patients with acute coronary syndrome (ACS) in our country,and the factors affecting the efficiency of medical intervention of pre-hospital care.Methods An epidemiological investigation with target population-based cross-sectional study was carried out,and specifically designed questionnaire for determining the efficiency of pre-hospital care of patients with ACS was used to collect information of 272 patients from 13 emergency pre-hospital care centers.Results After analysis of the data from 13 majormedical centers,it could be classified into 4 patterns of pre-hospital care,namely directive pattern,pre-hospital pattern,dependent pattern and independent pattern.The results of analysis showed that the distance for ambulance driving in directive pattern was shorter than that in dependent pattern,but the call-response in directive pattern was quicker than that in pre-hospital pattern and dependent pattern,while the call-arrival time in directive pattern was longer than that in independent pattern and dependent pattern.The analysis of the on-site preliminary treatment in four patterns of pre-hospital care showed that there were differences in the establishment of intravenous access,aspirin,nitrate and ECG ( P ＜ 0.05 ).The total effective rate of pre-hospital care for ACS was 48％,while effective rate of independent pattern reached 70％.Factors affecting therapeutic effect on ACS resulting in better outcomes included pre-hospital pattern ( OR =4.097 ),directive pattern ( OR =5.158 ),and use of nitrate ( OR =3.045 ) and oral administration of medicine ( OR =8.215 ). Conclusions Independent pre-hospital pattern had the best therapeutic effect in the pre-hospital care of patients with ACS,and pre-hospital pattern had the best on-site preliminary disposal.Use of nitrate and oral administration of medicine showed the best benefit to the therapeutic effect.