OBJECTIVE To study the immunization coverage and immune effects of hepatitis B vaccine (HepB) among people who were immunized later than at birth in Guangzhou city. METHODS A multistage randomized cluster sampling was used and the subjects were at age 20 to 59 years old, from the families of twelve districts in Guangzhou. Cross sectional analysis was carried out. Every study subject's HepB immunization history and main risk were investigated through questionnaire. Venous blood samples were collected and then tested for HBsAg and anti-HBs by means of ELISA. The immunization coverage rate of HepB, prevalence rates of HBsAg and anti-HBs among every age group were valuated by sampling weights. The protective efficacy of the people with immunization of HepB was assessed by case-control study. RESULTS The overall immunization rate of HepB was 24.71% (95%CI: 20.86%-28.56%) in the 20-59 age group. HBsAg prevalence rate was 14.91% (95%CI: 12.73%-17.08%), and 8.52% in vaccinated group while 18.15% in the non-vaccinated group. Results from case-control study showed that HepB had good protective efficacy to HBV in people of 20-59 years old. The protective rate of HepB against HBV was 62.6%. CONCLUSION Vaccinating HepB on people after the neonatal period also non-newborn could provide good immune effect to HBV.