The effect of aging temperature on the microstructure and tensile properties of 2198 Al-Li alloy were investigated by tensile test and TEM. The results show a great dependence of tensile properties on aging temperature in a narrow temperature region before peak aging. When the temperature (150 °C~170 °C /14 h) increases, the tensile strength rises dramatically; meanwhile the tensile elongation decreases. The main precipitates detected in 2198 alloy are δ′, θ′, β′/δ′, T-1 and σ phase. The combination and morphology of precipitates vary with different aging temperatures; the main precipitates are δ′, θ′, β′/δ′ when aging below 160 °C, while above 160 °C, T-1 and σ phases come out in large numbers, and become the dominating strengthening phases gradually. It is concluded that the sensitivity of 2198 Al-Li alloy to aging temperature is essentially attributed to the variety and amount of precipitates