Abstract: This paper takes into full account of the sedimentary age and environment, soil-type and characteristics and other factors from the geological survey in Suzhou City. It then divides the engineering geological strata groups of soil mass on the eastern plains area. It further identifies the key bearing strata group and weak-sensitive strata. A free piston thin wall sampler and frozen snapping-paste method are used to obtain undisturbed specimens for miro-structure analysis. It uses the analysis of digital images by Scanning Electron Microscope. The comparative studies on the micro-structure properties are carried out to analyze the microstructure type classification under undisturbed natural state, particles' orientation characteristics, eccentricity, orientation probability entropy and other quantitative indicators.that the following results are found. The angle distribution range between the x-axis and the horizontal long axis was relatively concentrated for particles, which means that the degree of anisotropy is relatively low. In addition, shallow marine depositional environments, as well as the transgressive and regressive hydrodynamic effects from Late Quaternary could make the seventh soft layer's distribution probability of eccentricity in(0.6, 1.0) and the orientation probability entropy relatively high. These results are useful to better understand the basic engineering properties of the soft soil in Suzhou city, and to providing important experimental data for establishing the relationship among the sedimentary environment, micro-structure and macro-engineering properties of soils.