A copper butt welding test is conducted using laser scanning welding technology to investigate its impact on the quality, mechanical properties, and electrical conductivity of copper welded joints with varying plate thicknesses. This investigation is conducted by altering the laser scanning trajectory. The results indicate that, compared with the linear scanning trajectory, the “O”, “8”, and “∞” scanning trajectories demonstrate improved weld formations across different plate thicknesses. These improvements are accompanied by significant increases in both tensile strength and electrical conductivity. The “O” scanning trajectory shows the most significant improvement, with its optimal weld formation and good stability of its molten pool. The tensile strength and electrical conductivity reach maximum values of 226 MPa and 72.46 MS/m in the penetratedand state, while 232 MPa and 69.44 MS/m in the unpenetrated state. Compared with the linear scanning trajectory, the improvements are 24.86%, 24.63%, 15.42% and 22.21%, respectively. Therefore, selecting the appropriate scanning trajectory can effectively improve the appearance and morphology of copper welds as well as enhance the quality of welded joints, mechanical properties, and electrical conductivity.