Abstract: Influence of laser prepulse on ultra-short laser-driven proton acceleration was investigated by different spatial distributions and energy spectra between different foil-targets, and spatial distribution and energy spectrum were measured at the normal direction of target rear according to the target normal sheath acceleration (TNSA). The laser wavelength is 744 nm and peak focal intensity is about 6×10¹⁶ W/cm². Proton amount increased with decreasing the target thickness, but the divergence angle also increased with decreasing the target thickness as a result of the target surface-shape destroyed by the laser prepulse. The energy spectra recorded by a Thomson mass spectrometer were also influenced by the decrease of hot electron recycling attributed to the destroyed surface-shape. The results show that the foil target in the laser-driven proton acceleration experiments can not be too thin.