Abstract: Based on the study of the flow maldistribution in plate-fin heat exchanger,the effect of header configuration on thermal performance and reduction of heat exchanger efficiency caused by the flow maldistribution in heat exchanger was experimentally studied.The experimental results showed that the effect of header configuration on the flow and temperature distribution in heat exchanger was significant.An improved header configuration not only could decrease the time from starting to steady working condition of heat exchanger，but also make the flow and temperature distribution more uniform in heat exchanger.At the same time，the correlation between heat exchanger efficiency and flow maldistribution characteristics was deduced from the experimental data.