Abstract: Objective To understand the incidence pattern of adverse event following immunization (AEFI) and identify the related factors, and provide evidence for the improvement of the quality of vaccination services. Methods The incidence data of AEFI in Taizhou during 2012 were collected through national AEFI information management system and the descriptive epidemiological analysis was conducted. Results Totally 173 AEFI cases were reported in 2012 through AEFI information management system in Taizhou. AEFI were reported in all 9 counties, the overall reporting rate within 48h was 98.27% and the investigating rate within 48 hours after reporting was 100%. Among the 173 cases, 112 were children less than 1 years old, accounting for 64.74%; Among the AEFI cases, 136 were mild reactions, 26 were abnormal reaction, 10 were joint reactions and 1 was psychogenic reaction, accounting for 78.6%, 15.0%, 5.8% and 0.58% respectively. AEFI occurred within 1 day after vaccination in 157 people, accounting for 90.75%; Among the AEFI cases, 172 were cured, accounting for 99.4%. Conclusion AEFI surveillance system in Taizhou worked well. The reporting rate, investigating rate within 48 hours and the sensitivity of AEFI surveillance were at high levels. The vaccination safety and service quality were ensured.