Abstract: Shale has extremely low permeability and could be used as a caprock for CO₂ geological storage. The mechanical properties of shale change under the CO₂-fluid long-term interaction, which directly affects the sealing performance of shale caprock. Based on this, to study the effect of supercritical CO₂-brine on the tensile fracture characteristics of shale, supercritical CO₂-brine is used to saturate the Longmaxi shale for 15 days and 30 days under the conditions of 110 ℃ and 30 MPa, respectively, and the Brazilian splitting tests are conducted on shale before and after supercritical CO₂-brine saturation. Meanwhile, the continuous deformation and fracture process of shale is monitored in real time by combining acoustic emission （AE） and digital image correlation （DIC） techniques. The results show that the non-uniform damage of shale caused by supercritical CO₂-brine interaction can easily induce multiple local fractures, which is manifested as a large number of discrete point-like or strip-like strain concentration areas during the loading process. In addition, with the increase of supercritical CO₂-brine saturation time, the shear fracture phenomena increase significantly, and the fracture mode gradually changes from tensile fracture to tension-shear mixed fracture. Supercritical CO₂-brine interaction increases the complexity of shale fractures, and the fracture morphologies change from a straightly single fracture to a curved fracture band. After supercritical CO₂-brine saturation, microstructural changes such as the generation of dissolution pores and microcracks and expansion of clay and organic matter in shale directly lead to a significant weakening of tensile fracture properties, and the longer the saturation time, the greater the reduction. Compared with the dry shale, the tensile strength of shale saturated with supercritical CO₂-brine for 15 days and 30 days decreases by 40.18% and 48.21%, the initiation stresses decrease by 17.72% and 37.99%, and the damage stresses decrease by 35.54% and 58.36%, respectively. The study has clarified the weakening law of the tensile fracture properties of shale under supercritical CO₂-brine long-term interaction, which can provide a reference for CO₂ geological storage.