The deviations of wedge angles to some extent between the actual value and accurately theoretical value are made purposely during processing the segmented wedge array line focussing system in order to improve the large-scale nonuniformity caused by unit diffraction. In this paper, theoretical calculation and experimental verification are made, and the reasonable deviation datu are given in the case of improving the uniformity while ensuring certain utilization ratio of line focus energy. It provides a necessary basis for the optimization design of uniform line focus system.