Owing to the special dual phase structure and high N content of duplex stainless steel, hot-working performance is poor, which is also a significant factor complicating its production. Therefore, a short process of direct cold rolling following solution treatment of the casting billet is proposed in this study. In addition, the synergistic deformation behavior of multiphase during the deformation of LDX 2101, as well as the action mechanism of the transformation-induced plasticity (TRIP) and twinning-induced plasticity (TWIP) composite deformation mechanisms in austenite is investigated. Further, the strain-hardening and fracture mechanisms of LDX 2101 are investigated using in-situ electron back-scattered diffraction (EBSD). The results indicate that when the strain is small (epsilon < 0.2), the TWIP effect dominates, and the deformation twins contribute to the strain hardening rate. Conversely, when the strain (epsilon >= 0.2) is increased,the strain distribution in metastable austenite increases and the stability decreases. Meanwhile, the TRIP effect can be induced by the deformation twins. Furthermore, as martensite's nucleation position increases, the TRIP effect begins to dominate. As a result, austenite does not complete the transformation of martensite during the early stages of deformation, but rather during the middle and late stages, delaying the generation of necking and improving the elongation. Therefore, the reason for LDX 2101's high strength and elongation can be attributed to the synergistic effect of TWIP and TRIP. However, the twin formation is selective. Additionally, cracks are most frequently found at the alpha/alpha ' interface and at the torsion of the shear bands within the ferrite grain. Consequently, LDX 2101 failed due to the propagation and bonding of open cracks.