Background The correlation between the plasma D-dimer level and deep vein thrombosis has not been conclusive in various studies.The aim of this research was to study the relationship between plasma D-dimer levels and the severity of orthopedic trauma by retrospective examination of orthopedic trauma cases.Methods Clinically acute trauma and non-acute trauma patients were selected and their plasma D-dimer levels were measured.Plasma D-dimer levels in patients of these two groups were compared.The relationship between the plasma D-dimer level and the severity of the trauma was also studied.Results There were 548 cases in the acute trauma group and 501 cases in the non-acute trauma group.The levels of plasma D-dimer were significantly higher in the acute trauma group than in the non-acute trauma group (P ＜0.01).In the acute trauma group,the correlation between the D-dimer level and the number of fractures was a positive linear correlation (r=0.9532).Conclusions Elevated plasma D-dimer is common in trauma patients.The D-dimer level and the number of fractures in the trauma patients are closely correlated.D-dimer is not only an indicator for the diagnosis of deep vein thrombosis and pulmonary embolus,but also an indicator of the severity of trauma in acute trauma patients.