Abstract: Based on the nanoindentation technique, the effects of aging treatment on the microstructure and mechanical properties of 2A43 aluminum alloy were systematically studied. Optical metallography（OM）, transmission electron microscopy（TEM）, X-ray energy dispersive spectroscopy（EDS） and scanning electron microscopy（SEM） were used to compare the changes of 2A43 aluminum alloy in two states. The results show that the hardness and elastic modulus of the original 2A43 aluminum alloy and the aluminum alloy after T6 heat treatment decrease with the increase of the load. More dimples are formed on the surface of the aluminum alloy after heat treatment, because the alloying elements are precipitated and small dispersive phases are formed after aging treatment, forming a hardening phase, and these hardening phases strengthen the aluminum matrix. At the same time, the aluminum alloy after aging treatment still has good structural uniformity, and its hardness significantly increases compared with the original 2A43 aluminum alloy.