Objective To evaluate the prognostic effect of different ratios of fresh frozen plasma (FFP) to packed red blood cells (PRBC) in massively transfused trauma patients.Methods A retrospective cohort study was conducted for 210 trauma patients who received more than 10 units of PRBC during the initial 24 hours from January 2007 to June 2015.The patients were divided into four groups:Group A(PRBC:FFP ≤1,n=41),GroupB (1 ＜PRBC:FFP≤1.5,n=63),GroupC(1.5＜PRBC:FFP≤2,n=30) and Group D (PRBC:FFP ＞2,n =76).At 24 hours after admission,blood transfusion amount,blood transfusion ratios,post-transfusion adverse reactions (allergy,non-hemolytic febrile transfusion reaction,hemolysis,congestive heart failure,pulmonary edema,etc) and coagulation changes [hemoglobin (Hb),platelet count (PC),prothrombin time(PT),activated partial thromboplastin time(APTT),international normalized ratio (INR),etc] were compared among groups.Prognostic markers including sequential organ failure assessment(SOFA),hospital stay,ICU stay,30-day mortality and causes of death were also evaluated.Results Use of PRBC was decreased significantly in Group A than in other groups (P ＜ 0.01),and there were no differences in blood transfusion adverse reactions among all groups (P ＞ 0.05).The coagulation indices (PT,APTT and INR) in Groups A and B were significantly decreased compared to Group D after transfusion (P ＜ 0.05).There were no differences in length of hospital stay and ICU stay among all groups (P ＞ 0.05).Group D was associated with higher SOFA and higher 30-day mortality than other groups(P ＜0.01),but no differences were found in Group A,B and C (P ＞0.05).Meanwhile,ratio of patients died of massive hemorrhage in Group D was also higher than other groups (P ＜0.01).Kaplan-Meier survival analysis showed the survival interval was the shortest in Group D,while the longest in Group B and C.Conclusions Modest transfusion ratios (1.5 ＜ PRBC:FFP ≤2)within 24 hours can substantially improve outcomes in trauma patients.Aggressive ratios may improve coagulation indices and reduce use of PRBC,with no more benefit to the outcomes.