Abstract: Objective To analyze occurrence features of adverse events following immunization (AEFI) and evaluate the operating quality of AEFI information management system and the immunization safety in Guangdong Province during 2011—2012. Methods AEFI data reported from January 1, 2011 to December 31, 2012 were collected through the National AEFI Information Management System.Records of vaccination in the same period were sourced from the monthly vaccination reporting system of Guangdong Province.The descriptive method was used to analyze the AEFI occurrence features.Results A total of 9 753 AEFI cases were reported (reported incidence rate, 89.77 per million doses)，of which 60.96% 5 945/9 753）were males and 39.04%（3 808/9 753）were females, 65.75% (6 413/9 753) were aged one year and under and 32.29% (3 149/9 753) were aged 2-7 years.Of all the AEFIs, 63.68% (6 211/9 753) were general reactions (mean reported incidence rate, 57.17 per million doses), 30.44% (2 969/9 753) were abnormal reactions (mean reported incidence rate, 2 733 per million doses), and 1.98% (193/9 753) were serious abnormal reactions (mean reported incidence rate, 1.79 per million doses).Symptoms of general reactions were mainly fever, redness and swelling, or indurations.Anaphylactic rash (2 399 cases), angioedema (125 cases), and lymphadenitis of Bacilli Calmette-Guerin vaccine (BCG) (137 cases) accounted for 89.63% (2 661/2 969) of all the abnormal reactions.Anaphylactic shock (57 cases), thrombocytopenic purpura (20 cases), and allergic purpura (16 cases) accounted for 48.19%(93/193) of serious abnormal reactions.Of all the AEFIs, 87.41% (8 525/9 753) occurred within 1 day after vaccination, and 97.75% (9 534/9 753) were cured or improved.Of all the diagnostic conclusions of abnormal reactions, 92.49% (2 746/2 969) were provided by investigation teams of institutions for disease control and prevention, 89.59% were provided by institutions for disease control and prevention at county level.Conclusion The sensitivity of AEFI surveillance in Guangdong was high.AEFIs often occurred among young group, within 1 day after vaccination, and with favourable prognosis.