Chemical contamination not only can cause environmental problems but also lead to a notable change in the mechanical properties of soil. Loess distributed over NW China is featured with metastable structure, and chemical contaminants induced by rapid urbanisation in recent years notably threaten the fragile loess environments. The microscale structural characteristics of the loess and the impacts on the macroscale mechanical properties, when exposed to chemical contaminants, are deemed critical for chemical-contaminated land reclamation. In light of this, the microscale structural characteristics of the loess specimens exposed to acetic acid and sodium sulfate respectively are studied using scanning electron microscopy, X-ray diffraction, and energy dispersive spectroscopy analyses. Further, their macroscale mechanical properties are determined by direct shear tests. The mechanism to lead to the microscale structural deterioration, when exposed to chemical contaminants, is revealed; the corrosion of the cement between particles caused by hydrogen ions when subjected to acetic acid environments and the salt-induced swelling phenomenon under saline conditions play a leading role in the microscale structural deterioration. The resultant macroscale mechanical properties show excellent correspondence with the deteriorated structural characteristics. The findings of this work provide key guideposts for chemical-contaminated land reclamation in NW China.