Abstract： Objective To compare the superiority of abbreviated injury scale (AIS) 2005 and AIS 1998 for evaluation of maxillofacial injury severity and major trauma outcome. Methods A total of 450 trauma patients evaluated by AIS 2005 and AIS 1998 from July 2005 to January 2007 were analyzed retrospectively. Results The mortality and morbidity of complications in trauma patients were ascending with the increase of injuries severity score (ISS). The ascending tendency in mortality was more notable in injuries severity score (ISS) > 20 in AIS 2005. The mortality in trauma patients in AIS 2005 was significantly lower than those in AIS 1998 in ISS > 15, < 20 ( P = 0.001 ). The ascending tendency to morbidity of complications was more notable in other ISS groups in AIS 2005 than those in AIS 1998. Conclusions The evaluation of injury severity and major trauma outcome by ISS based on AIS 2005 is superior to based on AIS 1998. It is reasonable to definite severe trauma by ISS value greater than 20 in AIS 2005.