Aiming at the problem of deformation of titanium alloy thin plate welding, a coaxial dual-beam laser composed of continuous laser and pulsed laser was used to test the welding of 1.5 mm thick Ti–6Al–4V thin plate. The effect of different laser power ratios, pulse widths, and frequencies on weld formation and sheet deformation is investigated, and the optimum welding process parameters for butt welding of Ti–6Al–4V sheet are determined. The test results show that the welding process parameters of continuous laser power of 1.6 kW, pulsed laser power of 0.3 kW, pulse frequency of 25 Hz, pulse width of 6 ms, and welding speed of 1000 mm/min can obtain a weld with excellent quality and the deformation angle of 0.9°. The tensile strength of the welded joint is 948 MPa, reaching 92.3% of the base material; the maximum residual compressive stress on the weld surface is 207 MPa, and the microhardness of the weld zone and the heat-affected zone is higher than that of the base material.