We　present　a　coaxial　laser　metal　deposition　(LMD)　system　based　on　the　single　mode　laser.　The　influence　of　input　beam　diameter　on　the　ring　spot　properties　such　as　spot　shape,　filling　factor　and　ring　width　are　investigated　through　numerical　simulation.　The　result　shows　that　the　smaller　ring　spot　and　narrower　ring　width　can　be　obtained　by　adopting　the　single　mode　laser　in　the　coaxial　LMD　system,　compared　with　the　traditional　coaxial　LMD　system　based　on　the　multimode　laser　(Flat-top　beam).　This　also　indicates　that　our　system　has　advantages　in　the　application　of　high-precision　additive　manufacturing　(AM).　©　2021　SPIE.