OBJECTIVE: To assess the prevalence rate of Helicobacter pylori (H. pylori) in blood serum, its affecting factors and isoforms (CagA,VacA )infection in the elderly people in Beijing. METHODS: 2006 residents were investigated through household questionnaire in different areas of Beijing (urban, suburban and mountainous district), who were older than 60 years old. Serum H. pylori CagA, VacA and Ureas antibody was detected by immunoblotting. RESULTS: The total H. pylori infection rate was 83.4% and the infectious rate of I form pathogenic H. pylori was 56.0%. The incidence rate in urban or suburban district was higher than that of in mountainous district (P < 0.001). I form H. pylori infection rate in people with heavy labor or young elderly were higher than that of intelegent work or older elderly (P < 0.05 ). I form H. pylori infection rate in people of low diet was higher than that of high protein diet (P < 0.001). CONCLUSION: The rate of H. pylori infection in blood serum was high among the elderly people in Beijing with most of it belonged to type I . However, significant differences were noticed on the distribution of isoforms in different age groups, areas, professions and diet habit.