<p>The influence of the degradation of organic pollutants from domestic sources on the geotechnical properties of clay soil is the basis and premise of scientific evaluation and engineering treatment of domestic source polluted soil sites. Through indoor geotechnical tests, using glucose as a representative domestic source of contaminant soluble sugar, the main objective of this study is to investigate the effect of soluble sugar degradation on the physical properties of clay. We can conclude that the physical characteristics of clay are significantly impacted by the anaerobic decomposition of soluble sugar. Although the anaerobic degradation of glucose reduces the clay’s strength, the undegraded soluble sugar has the opposite effect. Three key mechanisms that affect the physical characteristics of clay are “the formation of a hydrogen bond between glucose and clay pore water,” “the degradation of CO₂ to degrade clay structure,” and “the generation of carboxylic acid organic matter to dissolve alkaline oxides in the clay.” A folding pattern of change in the physical properties of contaminated clay results from the anaerobic decomposition of glucose, which can be separated into two primary stages: “ethanol and CO₂ production” and “carboxylic acid organic matter production”.</p>