New　types　of　ferrite　and　austenite　heat-resistant　steels　used　in　supercritical　or　ultra　supercritical　boilers　have　issued　challenges　to　conventional　welding　techniques.　As　a　reliable　and　advanced　joining　technique,　laser　welding　may　be　one　of　the　promising　solutions　for　the　welding　of　these　steels　due　to　the　low　heat　input.　A　slab　CO2　laser　with　an　output　power　of　3500　W　was　applied　and　the　narrow　gap　laser　welding　process　was　adopted　with　T-HR3C　filler　wire　to　weld　HR3C　tubes　of　the　new　type　austenite　steel　with　a　thickness　of　10　mm.　The　joint　microstructure　and　high　temperature　lasting　strength　were　investigated.　It　is　found　that　a　sound　joint　can　be　obtained　by　optimizing　the　process　parameters.　The　microstructures　in　the　weld　bead　are　fine　column　austenite　grains　with　a　few　fine　equiaxed　austenite　grains,　appear　more　or　less　symmetrically　along　the　bead　center.　The　grain　size　in　the　HAZ　is　not　obviously　coarsening.　The　micro-hardness　in　the　weld　is　correspondence　with　that　of　the　base　metal,　and　no　obvious　softened　zone　is　observed.　The　high　temperature　lasting　strength　of　the　laser　welded　joint　in　the　as-welded　condition　is　distinctly　improved　compared　to　that　of　TIG　welding　joint　with　post-weld　heat　treatment.