During the additive manufacturing process of T-shaped structure, it is prone to the problems such as poor metallurgical bonding and remelting defects at the intersections, which restrict the improvement of the performance. In this paper, T-shaped structure of Al – Cu alloy was fabricated by the laser–arc hybrid additive manufacturing. The microstructure at the intersections were characterized, and the temperature field and flow characteristics in the molten pool were analyzed by numerical simulation. The results show that the curved stripes caused by remelting can be observed at the intersections of the structure, and the simulated morphology of this region showed great agreement with the actual. The isotherm distribution was denser at the edge of the molten pool. The internal Marangoni convection led to the formation of counterclockwise vortices with a maximum velocity of 0.16 m/s. According to the differences of the grain morphology, it can be divided into the remelting zone of intersection (RZI) and the heat-affected zone (HAZ). RZI was mainly composed of fine dendrites, and the average grain size was 20.8% lower than that in HAZ. The precipitates were mainly the largesize θ (Al2Cu) phases which were incoherent with the α-Al matrix. The average microhardness can reach (98.4 ± 6.4) HV_0.1, which was up to 14.0% higher than that in the unremelting zone.