Abstract: Uneven medium flow in shell cover of plate-fin heat exchanger is the main factor lead to the degradation of heat exchanger performance. Through numerical simulation and laboratory test on gas-liquid two-phase flow in shell cover structure, analyzing the flow field in non-baffle shell cover, and according to the characteristic and discipline of the logistics distribution, an improved baffle structure with universal applicability is proposed. Through analyzing the sensibility of baffle place, baffle thickness and bore diameter, the baffle parameters are optimized. Comparing with other shell covers, the results show that the improved baffle structure has universal applicability, and can improve the medium flow in shell cover effectively. The flow standard deviation of exit passageway has reduced a magnitude compared with non-baffle shell cover, and reduced about 50% compared with staggered orifice type shell cover. This structure plays an important role in improving the heat exchange performance and reliability of the plate-fin heat exchanger.