The invention relates to a system and a method for improving the uniformity of a selective catalytic reduction (SCR) flow field. The system comprises a flue, a plurality of circular arc-shaped primary guide plates, a plurality of circular arc-shaped secondary guide plates, an ammonia injection grid, N tertiary guide plates, a plurality of catalyst layers, and M sets of differential pressure measurement components which are horizontally arranged along the width direction of the flue and are positioned between the catalyst layers and the tertiary guide plates, wherein each set of differential pressure measurement component is evenly provided with N differential pressure detection devices arranged at intervals along the depth direction of the flue. The system and the method can improve the flue gas flow field in front of the catalyst layers, guarantees the speed uniformity of an SCR system, and effectively reduces the phenomenon that the catalyst layers are blocked or worn.