Abstract： Objective A clinical analysis of early complications in patients with severe pulmonary hypertension(PH)undergoing congenital heart surgery with cardiopulmonary bypass(CPB)is reported.Methods A retrospective study of 45 patients with severe PH undergoing congenital heart surgery with CPB in our hospital from June 2003 to June 2009 was completed.The cause of death and the major complications in the early postoperative period were discussed.Results The major complications were severe hypoxemia,anoxic spell and low cardiac output.The mortality was 6.67%.The causes of death were all low cardiac output,which manifested decompensation of right ventricular function.By multivariate regression,Hypothermic CPB(OR=0.56;95%CI 0.35-0.89)was a risk factor for severe hypoxemia.Conclusion Early postoperative complications were mainly due to impaired function of heart and lungs,which based upon postoperative PH.Selective postoperative monitoring for pulmonary arterial pressure and right heart function,and prolonged mechanical ventilation for high risk patients may help to guide treatment and to prevent and cure early complications in these patients.