Abstract: The effects of hot-press on tensile properties and fracture morphology of AZ31B magnesium alloy welded joint welded by argon tungsten-arc welding were studied by tensile test, optical microscopy and scanning electron microscopy. The results show that the tensile strength and elongation of welded joint after hot-press were 200 MPa and 10%, respectively, and increased by 18% and 67% comparing with that of welded joint before hot-press. The tensile fracture of welded joint was mainly cleavage and more footmark platforms, accompanied by small amount of dimples. The fracture of hot-pressed joint showed the characteristics of quasi-cleavage fracture with plastic deformation flow lines, and the grains boundaries showed the phenomenon of sliding coordination.