To optimize the relationship of strength and ductility of an aluminum-lithium alloy, 2A97, a double-aging treatment was employed. The effect of double-aging processes on microstructures and tensile properties was investigated by transmission electron microscopy (TEM) and tensile tests. Results show that with the pre-aging temperature increasing, the formation of the strengthening precipitates T1 is promoted at the matrix at 155 oC, instead of the precipitation of θ"/θ′ and δ′ phases at 135 oC. It is different from that T1 precipitates nucleate and grow mainly at grain and subgrain boundaries at 135 oC. Numerous fine θ"/θ′ precipitates at the matrix at 135 oC cause the reduction of the width of θ"/θ′ precipitates-free zones adjacent to grain and subgrain boundaries and the size of equilibrium precipitates T1 at grain and subgrain boundaries. Numerous larger precipitates T1 dispersing homogeneously at matrix, combined with numerous large size θ′ and δ′ precipitates, yield higher tensile strength for the microstructure of double aging with 155 oC pre-aging than that of double aging with 135 oC pre-aging