Shortening the prehospital emergency medical services (EMS) response time is crucial for saving lives and lowering mortality and disability rates in patients with sudden illnesses. Descriptive analyses of prehospital EMS response time and each component were conducted separately using ambulance trip data from the 120 Dispatch Command Centre in the main urban area of Chongqing in 2021, and then logistic regression analyses were used to explore the influencing factors. The median prehospital EMS response time in the main urban area of Chongqing was 14.52 minutes, and the mean was 16.14 minutes. 44.89% of prehospital EMS response time exceeded 15 minutes. Response time was more likely to surpass this threshold during peak hours and in high population density areas. Conversely, lower probabilities of exceeding 15 minutes were observed during the night shift, summer and autumn seasons, and areas with a high density of emergency station. 33.28% of preparation time was greater than 3 minutes, with the night shift and high population density areas more likely to be greater than 3 minutes, while the summer and autumn seasons, and high GDP per capita areas had a lower likelihood of having preparation time greater than 3 minutes. 45.52% of travel time was greater than 11 minutes, with peak hours, summer and autumn, and high GDP per capita areas more likely to had travel time greater than 11 minutes, while night shift and high emergency station density areas had a lower likelihood of travel time greater than 11 minutes. The primary factors influencing prehospital EMS response time were shifts, traffic scenarios, seasons, GDP per capita, emergency station density, and population density. Relevant departments can devise effective interventions to reduce response time through resource allocation and department coordination, staff training and work arrangement optimisation, as well as public participation and education, thereby enhancing the efficiency of prehospital emergency medical services.