Purpose: This study was conducted to shorten the time spent at each stage of treatment and to reduce the total amount of time patients spend in the emergency department (ED) by applying Six Sigma in the treatment of major trauma patients. Methods: This is a comparative study encompassing 60 patients presenting to the ED of Bundang CHA Hospital from January 2008 to December 2008 and from July 2009 to March 2010. The stages of treatment for major trauma patients were divided into six categories (T1: total emergency department staying time, T2: duration of visit-radiologic evaluation time, T3: duration of visit-consult to department of admission, T4: duration of consultation-issue of hospital admissions time, T5: duration of visit-issue of hospital admissions time, T6: duration of issue of hospital admission-emergency department discharge time) and the total time patients spent in the ED was compared and analyzed for periods; before and after the application of Six Sigma. Results: After the application of Six Sigma, the numerical values in four of the six categories were significantly reduced; T2, T3, T4, and T5. However, the average of the total time patients spent in the ED did not show any remarkable change because the T6 increased highly. The level of Six Sigma increased $0.17{sigma}$. Conclusion: The application of Six Sigma for major trauma patients in the ED resulted in a significant improvement in the error rate for the total time patients spent in the ED. The Six Sigma activity has shown great potential. Therefore, the project is expected to bring better results in every stage of treatment if the levels of the hospital facilities are improved.