Objective To analyze the causes of blood transfusion incompatibility caused by a large number of blood transfusion and antiinfection in patients with car accidents and its influence on blood transfusion serology. Methods The clinical data of 120 patients with multiple injuries caused by traffic accidents from March 2016 to September 2019 were analyzed, retrospectively. Among them, 33 cases had crossmatch incompatibility, which belonged to the incompatibility group, and the rest were the control group. Collect relevant factors that may affect incompatibility, and use Logisticregression analysis to identify risk factors. Statistics of blood transfusion serology test results of patients with incompatible blood, and to analyze the influence of anti infection of massive blood transfusion on blood transfusion serology.Results The number of blood transfusions, time of using antibiotics, and the proportion of cephalosporin antibiotic applicationin the incompatible group were greater than those in the control group (P＜0.05). Logistic regression analysis showed that the number of blood transfusions, time of using antibiotics and the proportion of cephalosporin antibiotic application were the risk factors of blood mismatching (P＜0.001). The results of serological examination showed that the proportion of homologous antibody was the highest (54.55%), followed by abnormal protein agglutination (24.24%), positive direct anti human globulin (12.12%) and drug antibody (9.09%). Conclusion Blood transfusion times, antibiotic use time and cephalosporin antibiotics are the risk factors of blood matching incompatibility caused by massive blood transfusion anti infection in patients with multiple injuries caused by traffic accidents. The alloantibody, abnormal protein agglutination, direct anti human globulin positive and drug-induced antibody are the causes of blood matching incompatibility.