Introduction: To save lives and reduce the disability and death of the patients, emergency medical technicians (EMTs) must make timely decisions in complex and, sometimes, life-threatening situations. Since the pre-hospital decision-making is a continuous and important process. Objective: The present study aims to identify the factors affecting EMTs’ on-scene decision-making in emergency situations. Methods: A qualitative approach using in-depth semi-structured interviews and field observations was employed to explore the factors influencing EMTs’ on-scene decision-making in emergency situations. Purposeful sampling was performed with 19 participants including 12 EMTs, 3 dispatchers, 3 medical directions physicians and one EMS manager as a policy maker. Interviews were conducted from October 2018 to March 2018 and the data were analyzed using Graneheim and Lundman’ s content analysis approach. Results: Eight categories and 18 sub-categories emerged to describe the factors effective in emergency medical technicians’ on-scene decision-making. they were cultural context (community’ s culture and organizational culture), interactions (malingering, threat and violence and considerations), competencies (acquisitive and intrinsic); personal feeling (positive feeling and negative feeling), authority (structural and in processing), education (public and professional), special conditions (patient’ s clinical situation, weather conditions, mission’ s time and mission’ s location), and organizational resource (facility and equipment, and human resources). Conclusions: To facilitate EMTs’ on-scene decision-making, it is recommended to clarify the EMTs’ responsibilities, promote the community’ s culture, modify people’ s expectations, police monitoring and control and value the star of logo on EMTs' uniform. The EMTs’ on-scene decision-making process should also be explored.