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The evolution of surface microstructure of the poly crystals formed in TiAl alloy which is treated by laser shock processing is studied in this paper. After a single laser shock peening treated, there are some uneven distributed briefs in the pits formed on the surface of the sample was found, the relative height of briefs ranges from 100 nm to 300 nm and the raised edge is an annular boss. When the samples are treated with different energy density lasers, research on the protrusions showed that the numbers increased significantly and the relative height have an increasing tendency, and the average surface roughness of the pits increased obviously. Further study on the changes in shape of multiple impacts with the spot overlap rate of 50% reveals that the number of briefs significantly reduced compared with a single laser shock processing treatment, and the surface roughness is slightly increased. This is because the elastic deformation and plastic deformation tends to be saturated with the increase in the number of laser shock processing treatment, and the elastic deformation part gets rebound. The formation mechanism of the surface protrusions is analyzed, and the uneven plastic deformation flow model and shock wave superposition model are established. The surface topography formed by laser shock processing is the result of the coupling effect of the two models.