TC4 titanium alloy specimens are prepared via laser three-dimensional (3D) printing and the effect of solution-aging state on the microstructures and mechanical properties of the specimens is investigated. The experimental results show that an increase in solution temperature results in more obvious coarsening of the primary α phase. As the time in solution increases, more of the α phase transforms into the β phase. With respect to aging, as the temperature increases, the length and width of the secondary α phase precipitated from the residual β phase increase, and as the aging time increases, the volume fraction of the secondary α phase increases. During the aging treatment, the secondary reticular β phase is precipitated from the primary α phase, and the secondary α phase is precipitated from the β phase between the primary α phases. Owing to the precipitation of the two secondary phases, the properties of the specimens are affected. With treatment conditions at 950 ℃/1 h/WQ+550 ℃/4 h/AC, the TC4 titanium alloy shows the best mechanical properties. The room-temperature tensile strength is 990 MPa, the yield strength is 920 MPa, the elongation is 11.5%, and the area reduction is 27.5%. The fracture morphologies of the laser-3D printed TC4 titanium alloys in both the as-deposited and solution-aging states are laden with dimples and plastic fractures. Overall, the national standards for forgings have been met.