PURPOSE: To calculate Preventable Trauma Death Rate (PTDR), Trauma and Injury Severity Score (TRISS) is the most utilized evaluation index of the trauma centers in South Korea. However, this method may have greater variation due to the small number of the denominator in each trauma center. Therefore, we would like to develop new indicators that can be used easily on quality improvement activities by increasing the denominator. METHODS: The medical records of 1005 major trauma (ISS >15) patients who visited 2 regional trauma center (A center and B center) in 2014 were analyzed retrospectively. PTDR and PARK Index (Preventable Major Trauma Death Rate, PMTDR) were calculated in 731 patients with inclusion criteria. We invented PARK Index to minimize the variation of preventability of trauma death. In PTDR the denominator is all number of deaths, and in PARK Index the denominator is number of all patients who have survival probability (Ps) larger than 0.25. Numerator is the number of deaths from patients who have Ps larger than 0.25. RESULTS: The size of denominator was 40 in A center, 49 in B center, and overall 89 in PTDR. The size of denominator was significantly increased, and 287 (7.2-fold) in A center, 422 (8.6-fold) in B center, and overall 709 (8.0-fold) in PARK Index. PARK Index was 12.9% in A center, 8.3% in B center, and overall 10.2%. CONCLUSION: PARK Index is calculated as a rate of mortality from all major trauma patients who have Ps larger than 0.25. PARK Index obtain an effect that denominator is increased 8.0-fold than PTDR. Therefore PARK Index is able to compensate for greater disadvantage of PTDR. PARK Index is expected to be helpful in implementing evaluation of mortality outcome and to be a new index that can be applied to a trauma center quality improvement activity.