Femtosecond (fs) laser shock peening is a promising method for improving the surface properties of materials. In comparison to the traditional nanosecond (ns) laser shock peening, it offers superior precision, efficacy, flexibility, and processing speed, thanks to its ultra-high laser intensity and limited heat-affected zones. Due to the extremely strong ablation within an ultrashort period, the dynamics of fs laser-induced shock waves significantly differ from those of longer pulsed lasers. This study presents an investigation on the generation and propagation of fs laser-induced shock waves through a physics-based hydrodynamic model. The shock waves generated by a fs-laser can reach a peak pressure over 100 GPa, compared to ~3 GPa by a ns-laser. In addition, the fs laser-induce shock wave profile is substantially narrower with an extremely high pressure gradient, leading to a much higher strain rate (~109 s-1) than that (~106 s-1) by ns lasers. Despite the ultra-high peak intensity of the shock waves, no aggressive nano-size grain refinement is observed following fs laser shock peening, primarily due to the extremely short interaction time and high strain rate. The distinctive profile of fs laser-induced shock waves results in a rapid shock wave decay and, consequently, a significantly shallower layer with severe plastic deformation and enhanced mechanical properties.