OBJECTIVE The injury severity score (ISS) and new injury severity score (NISS) have been widely used in trauma evaluation. However, which scoring system is better in trauma outcome prediction is still disputed. The purpose of this study is to evaluate the value of the two scoring systems in predicting trauma outcomes, including mortality, intensive care unit (ICU) admission and ICU length of stay. METHODS The data were collected retrospectively from three hospitals in Zhejiang province, China. The comparisons of NISS and ISS in predicting outcomes were performed by using receiver operator characteristic (ROC) curves and Hosmer-Lemeshow statistics. RESULTS A total of 1825 blunt trauma patients were enrolled in our study. Finally, 1243 patients were admitted to ICU, and 215 patients died before discharge. The ISS and NISS were equivalent in predicting mortality (area under ORC curve [AUC]: 0.886 vs. 0.887, p = 0.9113). But for the patients with ISS ≥25, NISS showed better performance in predicting mortality. NISS was also significantly better than ISS in predicting ICU admission and prolonged ICU length of stay. CONCLUSIONS NISS outperforms ISS in predicting the outcomes for severe blunt trauma and can be an essential supplement of ISS. Considering the convenience of NISS in calculation, it is advantageous to promote NISS in China's primary hospitals.