Abstract: Metal-composite hybrid joints are widely used in aviation, ship, and automobile. Co-cured metal-composite joints with groove morphology can maintain the integrity of the composite structure and the continuity of fibers. ±45° grooves were designed on the connected metal surface, and the influence of surface morphology on the bonding performance of steel-glass fiber reinforced polymer (GFRP) joints was evaluated. The single-lap joint tensile shear test was designed to verify the shear performance of the bonded joints. In the simulation, the random Weibull distribution was introduced to define the material parameters of the cohesive element, and the progressive failure process of the joint was simulated combined with the vectorized user material (VUMAT) subroutine. The representative volume element (RVE) model of ±45° groove structure was established to analyze the influence of groove width and depth on the adhesive joint. The research shows that the ±45° groove structure can significantly improve the shear strength of steel-GFRP adhesive joints, and the numerical simulation strength and failure mode are consistent with the experiment. The influence of groove depth and width on structural bonding performance is obvious. The research in this paper can provide a reference for the design of metal-composite joints.