Abstract: Objective To analysis the role of more than 3 times blood transfusions in generation of irregular antibodies, and the impact of irregular antibodies in clinical transfusion. Methods The irregular antibodies in 1020 blood recipients who have been transfused more than three times were detected with saline method, polybrene method and micro-gel method. The relationship between the number of blood transfusions and irregular antibodies-positive rate and antibody type were analyzed. The effect of irregular antibodies in transfusion reactions and cross-matching of blood were observed. Results 26 cases of 1020 repeated blood transfusions patients were positive of irregular antibodies. The rate of irregular antibodies was positively correlated with the number of transfusions. The more of numbers of blood transfusion the more antibody types. The crossmatch time of irregular antibody-positive patients was 35+3.41 min, which was significantly longer than that of antibody negative patients (15+1.74 min). There were 2 cases of the 26 irregular antibody-positive patients occurred transfusion reactions, and the incidence of adverse reactions (7.69%) was higher compared to the antibody-negative patients (0.40%)．Conclusion More than 3 times blood transfusions increased the positive rate of irregular antibodies and antibody types. Antibody positive would prolong the time of crossmatch of blood, and increased the rate of transfusion reactions. Minimizing the number of blood transfusions and enhancing the detection of irregular antibodies are effective measures to prevent transfusion reactions and ensure the safety of blood transfusion.