During　the　formation　of　sub-wavelength　ripples,　the　initial　surface　plasmon　(SP)-laser　interference　plays　an　important　role.　In　this　Letter,　the　effects　of　grating　structures　on　the　distribution　of　the　absorbed　laser　intensity,　SP-laser　coupling,　free　electron　distributions,　and　ablation　shapes　are　investigated　by　the　plasma　model,　taking　into　consideration　both　the　laser　wave-particle　duality　and　the　transient　localized　changes　of　material　properties.　The　simulation　results　show　that　the　grating　structures　can　strongly　enhance　the　energy　absorption　and　SP-laser　coupling,　which　makes　the　fabrication　of　sub-wavelength　ripples　more　efficient.　It　is　also　found　that　the　ablation　shapes,　in　terms　of　ablation　depths　and　sub-wavelength　ripples　periods,　are　strongly　related　to　the　grating　structures,　which　can　be　used　to　control　micro/nanostructures　precisely　and　uniformly.