Objective:To determine the prevalence of Helicobacter pylori (Hp) infection in orthotopic liver transplantation (LT) recipients, and to study the efficacy and safety of Hp eradication therapy.Methods:13C-urea breath test was carried out between July 2018 and October 2019. There were 104 males and 26 females with an average age of 52.1 year for these LT recipients who were regularly followed-up in the Organ Transplant Center, the Affiliated Hospital of Qingdao University. Propensity scoring was used to match age and gender in a ratio of 1∶3. A healthy group of individuals consisting of 299 males and 91 females, with an average age of 51.8 years, were selected as the control group also in a ratio of 1∶3. All patients underwent 13C-urea breath test to evaluate Hp infection and results of quadruple therapy. Results:The prevalence of Hp infection among the LT recipients was 18.5%(24/130) which was significantly lower than the control group 36.4% (142/390) (χ 2=14.400, P<0.001). Among the recipients who received LT and 13C-urea breath test for less than 1 year, 1-3 years and more than 3 years, the prevalences of Hp infection were 14.3% (6/42), 17.8%(8/45) and 23.3%(10/43), respectively. Although the prevalence of Hp showed a gradually increasing trend, no correlation between Hp infection and duration from LT was observed (χ 2=1.321, P=0.517). Seventeen Hp positive recipients underwent Hp eradication therapy. The success rate of Hp eradication was 100.0%(17/17). Immunosuppressant concentration was monitored regularly in 10 patients. During Hp eradication, the blood concentration of immunosuppressant increased from 1.7 to 3.6 times, and the drug dosage was reduced to one half to one third of what it was before Hp eradication. Seven of these 17 recipients suffered from adverse effects caused by increased levels of blood concentration of immunosuppressants, including headache, hypertension, insomnia and irritability. Normal liver and kidney functions were observed during eradication. Conclusion:In this study, the prevalence of Hp infection among liver transplant recipients was 18.5%. The success rate of Hp eradication was 100% using bismuth-containing quadruple therapy. The dosage of immunosuppressant required to be monitored, and if necessary, adjusted during eradication to reduce adverse side effects.