This study investigated a posttraumatic stress, social support, and work burden and identified related factors which exerted influence on posttraumatic stress of new firefighters. Data were gathered from total of 144 new firefighters. Also, 22 PTS items, 20 work burden items, and 8 social support items were analyzed by SPSSWIN 21.0 program. Posttraumatic stress according to general characteristics showed significant difference in gender(t=-2.57, p=0.01), experience of self danger(t=3.06, p=0.00), experience of rescuee danger(t=2.41, p=0.02), and experience of colleague danger(t=3.43, p=0.00). High risk group of PTS was 20.1%. Posttraumatic stress, social support, and work burden showed significant difference in the high and low risk group. Posttraumatic stress was correlated with work burden(r=0.34, p=0.00), social support(r=-0.29,p=0.00). Factors influencing PTS were Experience of colleague danger(${eta}$=1.274, 95% CI=0.08-0.96), social support(${eta}$=-0.090, 95% CI=0.85-0.98) and work burden(${eta}$=0.057, 95% CI=1.02-1.10). We need to reduce the work burden caused by influencing variable of traumatic stress and create more preventive discipline of traumatic stress for the new firefighters to improve the social support at work or home. Also, posttraumatic stress has to be managed consistently with support by changing the social attitudes and we need to seek the new system that anybody can get a consultation of a specialist.