Objective To access the effectiveness of modified early warning score (MEWS) and acute physiology and chronic health evaluation Ⅱ (APACHE Ⅱ) in predicting the degree of injury and outcome for emergently admitted polytrauma patients.Methods In this single-center prospective study,266 polytrauma patients hospitalized from June 2012 to January 2013 were enrolled.MEWS and APACHE Ⅱ score were collected and compared for the rate of ICU admission,high dependency unit admission,outpatient therapy,death,and discharge within 30 days.Diagnostic and predictive performance of MEWS and APACHE Ⅱ were assessed by the receiver operating characteristic curve (ROC).Results A higher values in MEWS and APACHE Ⅱ were linked to much severe injury,increased likelihood of admission to the ICU or high dependency unit and high mortality.Patients with MEWS value ≥5 had increased risk of death as compared with those with MEWS value ＜ 5 (x2 =90.749,P ＜0.01).MEWS =5,for injury severity evaluation,showed a sensitivity of 85.7％ and specificity of 84.8％.MEWS value≥5 predicted ICU admission with a sensitivity of 80.0％ and specificity of 91.1％ and high dependency unit admission with a sensitivity of 67.9％ and specificity of 79.9％.APACHE Ⅱ score ≥ 21 was associated with increased rate of death,with significant difference from that among patients with APACHE Ⅱ score ＜ 21 (x2 =73.518,P ＜ 0.01).APACHE Ⅱ score =21,for injury severity evaluation,showed a sensitivity of 90.5％ and specificity of 79.5％.APACHE Ⅱ score ≥ 21 predicted ICU admission with a sensitivity of 95.0％ and specificity of 73.6％ and high dependency unit admission with a sensitivity of 88.2％ and specificity of 72.8％.In prediction of prognosis,ICU admission and high dependency unit admission,area under the ROC curve with 95％ CI for NEWS was 0.889 (0.830-0.948),0.937 (0.900-0.975) and 0.946 (0.916-0.977) respectively and for APACHE Ⅱ was 0.939 (0.898-0.979),0.761 (0.677-0.845) and 0.832 (0.782-0.883) respectively.MEWS and APACHE Ⅱ score in death group were (6.4 ± 2.7) points and (29.9 ± 6.4) points,but lowered to (3.0 ± 1.5) points and (16.8 ± 5.7) points respectively in survival group (P ＜ 0.01).Conclusions Both APACHE Ⅱ and MEWS have the ability to discriminate the severity of polytrauma patients and identify the potential of seriously ill patients.MEWS is more suitable for early identification of critically ill trauma patient due to its easy and quick operation as well as low cost,while APACHE Ⅱ is more suitable for evaluation of emergency observing patients and ICU patients.