Aim To analyze the relation of serum sodium level with long-term prognosis in patients with heart failure and preserved ejection fraction.Methods We enrolled 562 consecutive chronic heart failure patients, who were divided into 3 groups according to serum sodium concentration on admission:＜135 mmol/L（hyponatremia group, n105,11.4%）, ＞145 mmol/L（hypernatremia group, n37, 4.0%）and 135 -145 mmol/L（normonatremia group, n783,84.6%）. The primary end point was all-cause mortality. Cox proportional-hazards regression modeling was used to evaluate the relation of serum sodium level to long-term outcome in patients with heart failure and preserved ejection fraction.Results Hyponatremia group patients were older, with more men, higher NYHA status, and faster heart rate, but lower systolic and diastolic blood pressure than other groups. The percentage of hypertension was higher in hypernatremia and normonatremia group. Hyponatremia group patients had lower red blood cells, hemoglobin, albumin, pre-albumin, cholesterol and chlorine, but higher end-systolic volume, serum creatinine, and urea nitrogen. During the median 3.7-year follow-up, there were 135 deaths （24.0%） for all causes, 30 in hyponatremia group （54.5%）, 2 in hypernatremia group （9.1%）, and 103 in normonatremia group （21.2%）. On multivariate COX regression analysis, hyponatremia group had the lowest survival （HR 2.158, 95% CI 1.237-3.766；P0.007） hypernatremia and normonatremia group had the similar survival.Conclusion In patients with heart failure and preserved ejection fraction, hyponatremia is a powerful predictor of long-term mortality, and hypernatremia and normonatremia have the similar survival.