Abstract: Microstructure and properties of the Fe-20Mn-3Cu-1.38C TWIP (twinning induced plasticity) steel TIG welding joint before and after solution treatment have been studied by uniaxial tensile test, microstructure observation, X-ray diffraction and microhardness test. The results revealed that the microstructure of welding joint without solution treatment was composed by coarse columnar crystals with specific orientation. Furthermore, a large number of granular carbides precipitated in weld zone and heat affected zone. After solution treatment, the isometric crystal was obtained and the precipitated carbide was dissolved completely. Meanwhile, the tensile strength of welding joint reduced from 953MPa to 870MPa, while the elongation increased from 41.85% to 66.35%. The microstructure and properties has been improved obviously after solution treatment. The tensile strength and elongation of base material is 1 100 MPa and 92.25% respectively. Both kinds of tensile samples fractured in the heat affected zone and the fracture appearance showed typical ductile fracture characteristic.