Abstract: A method of optimum design for a plate-fin heat exchanger based on genetic algorithm (GA) is put forward in this paper.Not only the structure of a heat exchanger can be optimized with this method,but also the optimal type selection of fins can be obtained in the case of many types of fins are given.For different requirements of design,weight or effectiveness of a heat exchanger can be taken as an object function respectively by GA.A database of fins has been set up for selecting the optimal type of fins easily,which includes the geometric parameters, heat transfer factors and friction factors of fins.These parameters can be directly applied to computer programs.Compared with the conventional optimization results,it is showed that the weight and the volume of heat exchanger optimized in this paper are both reduced.The optimizing software and the database of fins are universal and can be used for general optimum design of heat exchangers.