对于同时用电和热的生产工艺，热电联产是有效利用能源的方法之一。本文对带补燃余热利用的20MW燃气轮机热电联产在满负荷和50％负荷进行了热和Ex分析、经过计算给出能流图和格拉斯曼流形图。通过燃料利用率、电—热比率和第二定律效率对其进行评估、热电联产后，满负荷和50％负荷时的节能率分别为0．35和0．25。Ex损在燃烧室和余热锅炉炉内最明显。还给出热电联产在满负荷下的资金回收周期约为5年。 For both electricity and heat production processes, cogeneration is one way to make efficient use of energy. In this paper, heat and Ex analysis of 20MW gas turbine combined heat and power with after-combustion residual heat utilization were performed at full load and 50% load. After calculation, the energy flow diagram and the Grasman’s manifold diagram were given. The fuel efficiency, the electricity-heat ratio and the second law efficiency are evaluated. After cogeneration, the energy-saving rates at full load and 50% load are 0.35 and 0.25, respectively. Ex damage is most pronounced in the combustion chamber and waste heat boiler. Also gives cogeneration under full load capital recovery cycle is about 5 years.