To　analysis　the　mechanism　of　laser-induced　nanowelding,　the　near-field　enhancement　of　an　Ag　nanoparticle　dimer　system　which　is　irradiated　by　laser　was　calculated　based　on　a　finite　element　method　(FEM)　in　this　paper.　Meanwhile,　we　investigated　a　number　of　parameters　which　have　a　tremendous　impact　on　enhancement　factors,　such　as　the　gap　between　the　nanoparticles　and　the　polarization　and　wavelength　of　the　laser.　The　results　indicate　that　narrow　gap　between　Ag　nanoparticles　is　beneficial　for　generation　of　field　enhancement.　Only　the　vector　component　of　initial　electric　field　in　laser　along　the　dimer　axis　has　an　effect　on　the　electric　field　enhancement.　The　system　has　regular　responses　to　different　wavelengths.　There　are　three　peak　points　at　370,470,500nm　especially.　These　results　will　be　guidance　to　the　experimental　research　in　the　future.