Objective To investigate the correlation between the initial arterial blood lactic acid and Acute Physiology and Chronic Health Evaluation (APACHE) Ⅱ score in trauma patients and its value in prognosis. Methods From August 1st 2015 to July 31st 2016, the clinical data of trauma patients treated in Department of Emergency were analyzed retrospectively. All patients were divided into survival group and death group by observing 28-day prognosis. We compared the relationship between the initial blood lactate level and APACHEⅡ score, and analyzed the relationship between the above indexes and the prognosis of the patients. Results A total of 743 patients were enrolled, with692 in survival group and 51 in death group.The APACHEⅡ score and initial blood lactate level in the survival group [(9.93±4.62) points, (2.02±1.44) mmol/L] were significantly lower than those in the death group [(22.84±7.26) points, (4.60±3.69) mmol/L] with significant differences (t=18.20, 9.77; P<0.01). The APACHEⅡ score and the mortality rate of patients with lactic acid level >4 mmol/L were significantly higher than those of patients with lactic acid of 2-4 mmol/L and <2 mmol/L; the differences were significant (P<0.05). The blood lactate and mortality in patients with APACHEⅡ score >20 were significantly higher than those in the patients with ≤10 and 11-20; the differences were significant (P<0.05). There was a significant positive correlation between initial blood lactate level and APACHEⅡ score (r=0.426, P<0.01). Conclusions The initial blood lactate level and APACHEⅡ score of trauma patients are correlated with the severity of injury and mortality. Both of the increase of initial blood lactic acid level and APACHEⅡ score suggest the risk of death in trauma patients.