This study aimed to investigate the frequency of unexpected antibodies and evaluate the cumulative incidence of additional unexpected antibodies in Beijing. From January 1, 2011 to December 31, 2014, blood samples from 2,095 patients from 98 medical institutes in Beijing were sent to the Beijing Red Cross Blood Center for antibody identification. Of the unexpected antibodies, 29.5% were autoantibodies and 70.5% were alloantibodies. Anti-E was the most prevalent form of allo-antibodies (n = 445), accounting for 52.9% of the Rh system, followed by anti-M (76.6% of the MNS system) and then 142 cases of anti-C,e, 128 cases of anti-E,c, and 113 cases of anti-Lea. The cumulative incidences of additional antibodies were 0.55% (after the first transfusion), 1.82% (second time), 2.33% (fourth time), 3.07% (firth time), and 4.24% (seventh time). Antibody against the Rh system was the most prevalent, followed by antibodies against MNS, Lewis, Kidd, P1, and Duffy.