The evolution of microstructures and the properties of 2A66 Al-Li alloy during artificial aging was studied with differential scanning calorimetry (DSC), hardness measurement, tensile testing, scanning electron microscope (SEM) and transmission electron microscope (TEM). The results indicate that the strength can reach the peak value with the increase of aging time, and the higher the aging temperature, the shorter the time for peak value. The best aging process for peak value of 2A66 Al-Li alloy ages at 165 ℃ for 64 h and the alloy gets a good combination of strength and plasticity. Its hardness, σb, σ0.2 and δ are 146HB, 526.5 MPa, 448.9 MPa, 10.1%. The δ', θ' and T1 phases are the major precipitates of 2A66 alloy ageing at 165 ℃. At the early stage of aging, the main source of strengthening for the alloy is the GP zone, δ' phase and θ' phase. At the peak of aging, the θ' phase and T1 phase are the main strengthening phases.