The solid solution temperature affects the strengthening mechanism of thin-plate fine-grain 2A97 alloy with a grain size of less than 10 μm. It has been observed that the tensile strength of peak-aging 2A97 alloy obtained at 540 °C decreases by 40 MPa compared with 510 ℃ for the same solution time. X-ray diffraction， scanning electron microscopy， and transmission electron microscopy were applied to explain this phenomenon quantitatively from the perspective of strengthening mechanisms such as solid solution strengthening， grain boundary strengthening， dislocation strengthening and precipitation strengthening. It was found that the alloy solution-treated at 540 ℃ exhibited significantly grown grains， higher levels of recovery and recrystallization， lower dislocation density and wider grain boundary precipitate free zone than that at 510 ℃， resulting in a decrease in the properties.