Whether the anemia increases the risk of mortality in patients with acute heart failure (AHF) remains unclear. This study aims to explore the relationship between anemia and outcomes in patients with AHF including subgroup analysis. This study included 3279 patients with hemoglobin available from the Beijing Acute Heart Failure Registry (Beijing AHF Registry) study. The primary endpoint was all-cause mortality in 1 year, and the secondary endpoint was 1-year all-cause events including all-cause death and readmission. Logistic regression models were applied to describe related variables of anemia in patients with AHF. Multivariate Cox proportional hazards models described associations of anemia with clinical outcomes in the overall cohort and subgroups. 45.4% of the patients were found anemic. They were older and had more comorbidities than non-anemic patients. Variables including older age, female, chronic kidney dysfunction (CKD), lower hematocrit, lower albumin, with loop diuretics applied, without beta-blockers, angiotensin-converting enzyme inhibitors /angiotensin receptor blockers (ACEIs/ARBs) and spironolactone applied in the emergency department (ED) were associated with anemia in AHF patients. Anemic patients had higher 1-year mortality (38.4% vs. 27.2%, p < 0.0001) and 1-year events rates (63.2% vs. 56.7%, p < 0.0001). After adjusted for covariates, anemia was associated with the increase of 1-year mortality (hazard ratio [HR] 1.278; 95% confidence interval [CI] 1.114-1.465; p = 0.0005) and 1-year events (HR 1.136; 95% CI 1.025-1.259; p = 0.0154). The severer anemia patients had higher risks both of 1-year mortality and events. In the subgroup analysis, the independent associations of anemia with 1-year mortality were shown in the subgroups including age < 75 years, male, body mass index < 25 kg/m2 and BMI ≥ 25 kg/m2, New York Heart Association (NYHA) functional class I-II and NYHA functional class III-IV, with and without cardiovascular ischemia, heart rate (HR) < 100 bpm and HR ≥ 100 bpm, systolic blood pressure (SBP) < 120 mmHg and SBP ≥ 120 mmHg, left ventricular ejection fraction (LVEF) < 40% and LVEF ≥ 40%, serum creatinine (Scr) < 133 umol/l, and with diuretics use, with and without beta-blockers use, without ACEIs/ARBs use in the ED. Anemia is associated with older age, female, CKD, volume overload, malnutrition, with loop diuretics, without beta-blockers, ACEIs/ARBs and spironolactone administration, and higher mortality and readmission in AHF. The risk associations are particular significantly obvious in younger, male, overweight, preserved LVEF, lower Scr, with diuretics and beta-blockers, without ACEIs/ARBs administration subgroups.Clinical trial No. ChiCTR-RIC-17014222.