A　CW　Nd:YAG　laser　with　an　output　power　of　1kW　was　used　to　join　the　pipes　of　brass　and　low　carbon　steel　with　a　thickness　of　2mm.　The　focused　laser　beam　with　a　diameter　of　0.3mm　irradiated　at　the　brass　pipe　side　of　the　butt　joint　and　the　brass　part　was　penetratingly　melted　by　the　laser　power　while　the　steel　was　still　kept　the　solid　state.　Thus　the　melted　brass　liquid　wet　the　solid　steel　to　form　a　brazing　joint.　This　process　is　called　laser　penetration　brazing　(LPB).　The　interfacial　characterizations　of　the　joint　were　investigated　by　metallographic　microscope,　SEM　and　EDS.　The　results　showed　that　the　solution　and　the　diffusion　of　the　element　had　occurred　along　the　interface　between　brass　and　steel　and　the　metallurgical　bonding　was　achieved.　The　deepness　of　the　interaction　layer　was　about　5μm.　The　data　of　hardness　test　indicated　that　the　microhardness　value　of　the　weld　bead　was　higher　than　that　of　the　brass　substrate.　The　failure　was　happened　at　the　brass　substrate　side　of　the　dissimilar　metal　joint　in　the　bursting　test.