Laser　trimming　has　become　one　of　the　powerful　tools　for　precise　manufacturing　of　alloy　resistors　that　are　widely　used　in　electrical　vehicles,　electrical　controlling,　and　in　appliances.　In　this　work,　the　influence　of　femtosecond　laser　trimming　is　compared　with　nanosecond　laser　trimming.　The　authors　found　that　lasers　focused　on　different　heights　relative　to　the　sample　surface　induced　significant　changes　in　surface　morphologies.　The　resistance　change　was　systematically　investigated　as　a　function　of　cutting　lengths　and　cutting　depths　of　different　laser　powers　for　both　lasers.　The　experiments　display　that　femtosecond　laser　trimming　has　a　higher　precision　of　the　resistance　adjustment　than　nanosecond　laser　trimming.　The　periodic　ripple　structure　by　the　femtosecond　laser　was　investigated　at　the　focus　position　above,　onto,　or　beneath　the　surface.　The　period　of　a　low　frequency　ripple　structure　(LFRS)　on　the　ablated　groove　bottom　is　about　600-700　nm　when　the　laser　focuses　just　right　on　the　surface　but　changes　to　490-560　nm　when　focusing　above　or　beneath　the　surface.　The　period　of　a　high　frequency　ripple　structure　is　about　100-380　nm　at　the　vertical　direction　of　LFRS.　The　period　of　low　frequency　ripple　on　the　outside　of　the　groove　is　smaller　than　that　on　the　groove　bottom　for　all　three　focusing　cases.　The　period　of　the　LFRS　is　not　sensitive　to　the　laser　power.　The　range　of　the　resistor　value　change　in　the　s-polarized　light　direction　of　the　femtosecond　laser　is　more　than　that　in　the　p-polarized　light　direction.