Abstract: The effects of deformation degree and thermal aging on the tensile properties,phase boundaries,local strain distribution,coincidence site lattice(CSL) boundaries and orientation distribution of duplex stainless steels were investigated by electron backscattered diffraction(EBSD). It is found that after thermal aging,the strength of duplex stainless steels enhances and the ductility decreases. The number and density of small-angle boundaries in ferrite grains increase slightly under large deformation conditions.The plastic deformation ability and local strain in ferrite phases of the thermal aged materials decline. Large deformation destroys the original distribution of austenite and ferrite grains,as well as Σ3 twinning boundaries.