The aim of this paper was to address the effect of laser shock processing (LSP) on the microstructure of ultrafine-grained commercially pure aluminium which was produced through severe cold rolling and annealing. The microstructure characteristics of ultrafine-grained commercially pure aluminium were experimentally investigated by TEM during ultra-high strain rate loading. The results show that microstructure was obviously refined due to ultra-high plastic strain induced by a single pass LSP impacts. The grain sizes decrease from 0.6 μm after severe cold rolling and annealing to 0.3 μm at the center of the laser shock wave after a single pass LSP. There is a distinct increase in the dislocation density at the edge of the laser shock wave. These experiments have guide meaning to the practical engineering applications of LSP technique. The aim of this paper was to address the effect of laser shock processing (LSP) on the microstructure of ultrafine-grained commercially pure aluminum which was produced through severe cold rolling and annealing. The microstructure characteristics of ultrafine-grained commercially pure aluminum were experimentally investigated by TEM during ultra-high strain rate loading. The results show that microstructure was significantly purified due to ultra-high plastic strain induced by a single pass LSP impacts. The grain sizes decrease from 0.6 μm after severe cold rolling and annealing to 0.3 μm at the center of the laser shock wave after a single pass LSP. There is a distinct increase in the dislocation density at the edge of the laser shock wave. These experiments have the guide meaning to the practical engineering applications of LSP technique.