The invention relates to a thermal treatment method for improving fatigue crack spreading rate of 2xxx-T3 plates. The thermal treatment method is characterized by comprising the following steps: (1) burdening and smelting alloys and casting the burdened and smelted alloys into cast ingots; (2) performing uniform thermal treatment on the cast ingots: heating the cast ingots from room temperature to the temperature of 490-510 DEG C by an average heating rate of 10-400 DEG C per hour or for 1-48 hours, insulating for 1-60 hours, cooling down to the temperature of 470-500 DEG C after insulating, and insulating for 1-20 hours after cooling down to the temperature; (3) carrying out hot rolling, wherein rolling starting temperature of hot rolling is 470-490 DEG C, and hot finished rolling temperature is greater than 250 DEG C; (4) annealing and/or solution treatment; and (5) finishing treatment, and carrying out natural aging to obtain T3-state plates. Through cooling and high-temperature insulating after uniformization, namely technology application of uniformization and preheating and insulating integration, area fraction of second coarse phases in alloy tissues before hot rolling can be controlled effectively, so that fatigue crack spreading rate da/dN value of the 2xxx-T3 plates is improved remarkably.