The study enrolls 234 patients with type 2 diabetes and heart failure. The patients have an New York Heart Association (NYHA) functional class of II to IV, are randomly assigned to 2 groups. One group use exenatide , the other group is control group and each group has 117 patients. At the baseline, the 3rd day, the 28th day patients are required to complete the heart failure examination: plasma N-terminal pro-B-type natriuretic peptide(NT-proBNP), 6-min walking distance, echocardiographic measures, patient quality of life(MLHFQ). At the end of 4-week follow-up, we evaluate the efficacy of heart function improvements after treatment with exenatide and also investigate the mechanisms of exenatide improving heart function .