Abstract: A computational fluid dynamics (CFD) program FLUENT has been used to predict the fluid flow distribution in plate-fin heat exchanger.It is found that the fluid flow maldistribution is very serious in the direction of header length for the conventional header used in industry.Based on the analysis of the fluid flow maldistribution,two improved headers with a two-stage distributing configuration are recommended and predicted by CFD.The predictions indicate that the improved header configuration can effectively improve the performance of fluid flow distribution in the heat exchanger.The absolute degree of fluid flow nonuniformity in plate-fin heat exchanger has reduced from 3.47 to 0.71 by changing the header ocnfiguration.The computational results are in good agreement with experimental ones,which indicates that the CFD technology is capable of closely predicting the fluid flow distribution in plate-fin heat exchanger.