To evaluate the relationship between micromechanisms and different physical and chemical improvement methods on the seismic subsidence loess engineering site, soil samples were obtained along the Baoji-Lanzhou High-speed Railway, and dynamic triaxial and SEM microstructural tests were conducted. Combining image processing software with the appropriate threshold, the evolution law of microstructure deformation of samples was applied and studied. Results showed that:(1) Physical improvement is the most effective way to eliminate macropores and porous pore structures; moreover, the particle size distribution and structure can be also adjusted. (2) Chemical modification affects the strength of the loess from the aspect of particle contact and intergranular cementation; moreover, the participation of different chemical reactions can produce unique glass beads or flocculent fine structures, which can greatly reinforce the strength of loess and play a role in filling, cementing, or buffering in strong earthquakes. (3) The differences between loess microcosmic parameters and residual strain coefficients, with the above improved methods before and after strong earthquakes, were compared, and it was found that they are in good agreement, indicating that the microstructure can generally reflect the residual deformation strength of the loess.