The mechanical properties and microstructure of 2050 Al-Li alloy during non-isothermal aging (NIA) were investigated. The research results show that during the NIA heating stage (130 °C→220 °C), the strength of 2050 Al-Li alloy continues to rise. In the cooling stage (220 °C→130 °C), the strength of the alloy begins to decrease at 200 °C and reaches the minimum value at180 °C. When the temperature drops to 150 °C, the alloy strength reaches its maximum, and the yield strength (YS), ultimate tensile strength (UTS) and elongation are 544 MPa, 568 MPa and 9.8%, respectively. Microstructure studies have shown that during the heating stage of NIA, the volume fraction, average thickness and diameter of the T1 phase have been increasing. In the cooling stage, the average thickness and diameter of the T1 phase continue to increase, but the volume fraction begins to decrease. When the aging temperature drops to 190 °C, the average thickness and diameter of the T1 phase begin to decrease, but the volume fraction begins to increase. When it drops to 150 °C, the volume fraction of T1 phase, the average thickness and diameter are 8.7%, 2 nm and 26.5 nm, respectively. In addition, it is calculated that the critical thickness for the transformation of the T1 phase strengthening mechanism is 0.82 nm. Therefore, the main strengthening mechanism of the 2050 Al-Li alloy in the entire NIA treatment process is the Orowan bypass mechanism.