Abstract: Objective To examine the association between helicobacter pylori (HP) infection and the adverse prognosis at 1 year after onset of acute ischemic stroke (AIS).Methods From June 2011 to December 2013, first onset cases of AIS were collected from 14 hospitals in 7 provinces of China to establish research cohort. The venous blood sample of patients was taken to do HP-IgG content test within 24 hours after admission. The follow-up was conducted at 1 year after the onset of AIS, and the adverse prognosis outcome information was investigated and collected. Cox regression models were applied to estimate the association between different quartile levels of HP-IgG and different prognosis outcomes. Results A total of 1 150 AIS cases was conducted in the study. The M(P₂₅,P₇₅) of venous HP-IgG was 10.14(7.39,15.05) ng/L. Within 1 year after AIS onset, the incidence of all-cause death, cardiovascular events cardiovascular death and death or cardiovascular events was 4.83%, 7.90%, 3.72%and 11.43%, respectively. After adjustment for multiple factors, Cox regression model showed that the risk of all-cause mortality and cardiovascular death increased in G4 group compared to the G1 group, and the HR(95% CI) was 3.43(1.26-9.36) and 5.45(1.57-18.90), respectively; The risk of death or cardiovascular events increased in G2, G3 and G4 group compared to G1 group, and the HR(95% CI) was 1.84(1.02-3.34), 2.00(1.12-3.56) and 1.97(1.10-3.55), respectively; the 1 year risks of mortality and death or cardiovascular events were both increased with the level elevated in quartile groups, and the test of tendency was statistically significant (all P<0.05). Conclusions HP infection is the risk factor of AIS adverse prognosis. High HP-IgG level can increase the risk of mortality, cardiovascular death and death or cardiovascular event within 1 year after AIS onset.