This study is aimed to investigate the effect of various thermomechanical treatments(T_6, T_8 and ITMT) on the microstructure and mechanical properties of an Al-Cu-Li-Ag-Mg-Zr alloy (Weldalite 049) which has been known to strong natural aging response, good weldablity and high strength in T_6 and T_8 temper. This experiment was performed by means of differential scaning calorimetry, tensile test, optical and transmission electron microscopy. The tensile strength in the peak aged condition shows 620, 650 MPa in T_6 and T_8(40% cold work), respectively. Also, The tensile strength is increased with cold working in T_8 but decreased at 60% cold working. However, the tensile strength of the intermediate thermomechanical treated speciman(ITMT) is lower than that of T_6 temper about 20% but the elongation is higher than two times. It might be predicted that the ITMT is effective processing to improve the toughness of this alloy. In T_6, T_8 and ITMT, the major strengthening phase is T₁(Al₂CuLi) phases, and the fine T₁phase which are homogeneously precipited in matrix was observed much more in T_8 than T_6 and ITMT.