Abstract: The concept of loess structure improvement is put forward in this study. It refers to the concept that the collapsibility and seismic subsidence are poor engineering properties for loess, and their elimination is essentially the optimization or evolution of the loess intrinsic quality. On this basis, a chemical method to improve the loess structure is proposed, i.e., using acid to dissolve calcium carbonate to destroy the pore structure quickly and effectively. The structure evolution of collapsible loess under different pressures in different concentrations of acetic acid solution is observed and analyzed by the scanning electron microscope (SEM). The tests results indicate that the structure of loess is improved due to the acetic acid under low pressures, while the effect of acetic acid is not obvious under high pressures because of the previous complete elimination of the pore structure. In addition, the saturated compression tests and consolidated quick shear tests are carried out to verify the effect of the evolution of loess structure treated with acetic acid. The results indicate that the loess treated with acetic acid has a smaller possibility and perniciousness of secondary or multiple collapse and a higher shear strength under the same pressures. Finally, two practical applications of this research are put forward. One is that, if adding some acetic acid, the construction effect of pre-soaking method can be notably improved. The other one is that the research results can provide valuable reference for the geotechnical engineering construction on the loess polluted by acidic waste water and other related special studies.