Additive　manufacturing　(AM)　with　low　heat　input　is　a　crucial　technology　of　on-line　maintenance　of　long-distance　oil　&　gas　transmission　pipeline.　By　utilizing　two　methods,　i.e.　laser　and　cold　metal　transfer　(CMT)　arc,　with　low　heat　input　and　a　homemade　filler　wire,　the　AM　test　was　separately　carried　out　on　the　widely　used　X80　steel.　Parameters　and　the　overlap　ratio　of　AM　processes　were　optimized　at　first;　afterwards,　the　additively　manufactured　parts　(AMPs)　were　prepared　on　the　surface　of　the　X80　pipeline　steel　substrate.　Subsequently,　the　microstructures　of　the　AMPs　were　observed　and　also　microhardness　test,　impact　test　and　tensile　test　were　carried　out.　The　result　showed　that　the　heat　affected　zones　(HAZs)　of　the　substrate　were　both　not　softened　by　applying　the　two　methods.　The　microhardne　values　of　the　laser-　and　CMT-based　AMPs　were　separately　140%　and　119%　that　of　the　substrate,　respectively.　The　impact　energies　of　the　laser-　and　CMT-based　AMPs　at　room　temperature　were　53%　and　67%　that　of　the　substrate,　respectively.　The　average　tensile　strengths　of　both　laser-　and　CMT-based　AMPs　were　higher　than　that　of　X80　substrate,　while　the　average　percentage　elongations　after　fracture　of　laser-　and　CMT-based　AMPs　are　similar,　which　both　accounted　for　about　66%　that　of　the　substrate.　It　is　noted　that　the　mechanical　properties　of　the　laser-　and　CMT-based　AMPs　both　showed　anisotropy,　in　which　the　anisotropy　of　the　former　was　more　significant.　©　2020　The　Author(s).