Background: In the thermal-hydraulic design of molten salt reactor (MSR) with liquid fuel, the structure and the flow field distribution of lower plenum play a decisive role for the core flow distribution.Purpose: The mass flow distribution of core inlet is designed to match with the release heat distribution, so that the core power distribution will be flattened in radical.Methods: To realize the reasonable distribution of core flow, the flow field of lower plenum is optimized through adjusting the geometry of core lower plenum and flow distribution device using FLUENT software to simulate three-dimensional flow field of core.Results: The simulation results showed that the mass flow rate standard deviation of salt channels of trumpet-shape lower plenum is reduced by 4.2% compared with that of the ellipsoid-shape. The mass flow rate standard deviation of salt channel is reduced by 29.2% by setting the flow distribution plate.Conclusion:Changing the structure of lower plenum andsetting the flow distribution plate are useful measures to adjust the mass flow distribution and power matching. The results can provide the basis for the optimization design of MSR with liquid fuel.%在液态燃料熔盐堆(Molten salt reactor, MSR)热工水力设计中，为实现堆芯径向功率展平需对堆芯流量分配进行设计，使得堆芯进口流量分布正比于释热量分布，而下腔室结构和流场分布对堆芯流量分配起决定性作用。利用FLUENT软件对堆芯三维流场进行模拟，通过调节下腔室结构和流量分配装置，对下腔室流场分布进行优化，最终实现堆芯流量合理分配。数值模拟结果表明，喇叭状下腔室比椭球形下腔室熔盐通道流量标准差降低4.2%，设置流量分配板熔盐通道流量标准差降低29.2%；改变下腔室结构和设置流量分配装置能够较好调节流量分配和功率分布匹配性，该结果可为液态熔盐堆堆芯优化设计提供依据。
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