A　continuous　wave　(CW)　Nd:YAG　laser　with　a　output　power　of　1　kW　was　used　to　join　H62　brass　and　20#　low　carbon　steel　with　a　thickness　of　2　mm.　The　focused　laser　beam　with　a　diameter　of　0.3　mm　was　irradiated　at　the　brass　side　of　the　butt　joint.　Thus　the　brass　was　penetratingly　melted　and　interacted　with　the　solid　steel　to　form　a　brazing　joint.　The　brass　is　penetratingly　welded,　and　the　low　carbon　steel　is　brazed.　This　process　is　called　laser　penetration　brazing　(LPB).　The　interfacial　characterizations　of　the　joint　were　investigated　by　metallographic　microscope,　scanning　electron　microscope　(SEM)　and　energy　dispersive　X-ray　spectroscope　(EDS).　The　results　show　that　the　element　diffusion　and　solution　occur　and　metallurgical　bonding　is　achieved　between　brass　and　steel.　The　width　of　the　interaction　layer　is　about　3　μm.　The　brass　weld　is　harder　than　that　brass　substrate　and　the　failure　occurs　at　the　brass　substrate　but　weld　judged　from　the　data　of　bursting　test.　The　mechanic　performance　of　H62　brass　and　20#　low　carbon　steel　butt　joint　by　laser　penetration　brazing　can　meet　the　demand　of　industrial　application.