Under cluster sampling, an early serum essay of helicobacterpylori (Hp) infection among 1084 healthy people, was carried out. Out of them, 325 among the Yi and Han Nationalities at Yunxian County of Yunnan Province were given a simultaneous test of anti-HAV IgG. The results were as follows: overall Hp infection rate was 51.1%; no difference of the infection was observed between the Yis and the Hans; the prevalence of Hp antibody went up with age; Higher rates were detected among those who drank river water or unboiled-water than among those who drank tap water, well water or boiled water, from poultry raisers than from non-poultry raisers and with drug abusers than with non-drug abusers. Hp infection showed a parallel relation to HAV infection. Finally, seven main epidemic factors were sifted from multi-factor logistic analysis namely source of drinking water, drinking habit, chicken-raising, pig-keeping, dog-breeding, drug-abusing and consumption of garlic. All these findings suggested that drinking water was an important vehicle of Hp infection. Our research data seems to have lend support to both fecal- oral transmission viewpoint and the hypothesis that Hp infection derives from animals. Frequent intake of garlic may serve as an agent in long-term prevention of Hp infection among people in this area.