Abstract: The tensile properties of high carbon copper-bearing TWIP steel with different contents of non-metallic inclusions and distribution of size were compared to study the effect of non-metallic inclusions on tensile properties. The results show that non-metallic inclusions in the TWIP steel became the nucleation points of cavities under tensile load, leading to the early initiation of cavities. But the nucleation and growth of cavities were delayed because the TWIP steel was easy to form twinning and had high strain hardening rate. Besides, as a result of plastic fracture without necking, the tensile properties of the steel had a high level of tolerance for non-metallic inclusions. While the area fraction of the non-metallic inclusions in the TWIP steel raised from 0.171% to 0.394% and the surface density of the inclusions in equivalent diameter above 5 μm improved from 4 to 29, the various tensile properties such as tensile strength and elongation only reduced by 1% to 3%, showing good tensile properties.