Objective To investigate the influence of brain natrluretic peptide(BNP) in the prognosis of cardiac surgery.Methods Selected 115 cases of pafients with the first cardiac surgery.Their BNP concentration was measured before operation. Observed the relationship between BNP and postoperative atrial fibrillation,mechanical ventilation time,hospital stay,and the mortality of 30 d.Results Whether the patients had hypertension,diabetes,myocardial infarction history,left main stem disease and hemoglobin level or not,showed no definite relationship with BNP (P>0.05).Preoperative lower left ventricular ejection fraction (LVEF)(P=0.002) and European system for cardiac operation risk evaluation [(5±3)scores](P=0.003) were associated with higher BNP level.Postoperative mechanical ventilation time was(15.0±5.4)h,hospital stay was (32±11) d,showed a clear relationship with BNP(P= 0.035,0.001),but postoperative mediastinal infection,atrial fibrillation and mortality of 30 d had no definite relationship with BNP(P>0.05).Conclusion BNP can be used to predict the risk after cardiac surgery.