A novel method called thermomechanical treatment based on impact hydroforming (TTIHF) was proposed. The pre-deformation was achieved by using impact hydroforming (IHF) loading. The strengthening effect and mechanism of 2195 Al−Li alloy were investigated under various loading pre-deformation conditions. The results showed that the time for the alloy to reach peak aging was shortened under TTIHF. Compared with those of the pre-deformation method of stamping forming, the yield strength and tensile strength of the Al−Li alloy under TTIHF increased by 18.6% and 18.0%, respectively. The deformation caused by IHF loading resulted in a high density of dislocations, which served as nucleation sites for the precipitation of the T₁ phase during aging. After TTIHF, the average diameter and thickness of the T₁ phase in the alloy were smaller than those under other experiment conditions. Moreover, the density and distribution of the T₁ phase were the highest and the most uniform.