Abstract: Past studies have shown that the macroscopic mechanical properties and performance of soil depend on its microstructure essentially. Driving pile into a soft soil would cause a significant change in the internal structure of the soft soil surrounding the pile. The strength and deformation characters are the macroscopic expression of this change. The relationship between soil microstructure and its change of macroscopic mechanical behavior is of great theoretical and practical significance. It can not only reveal the mechanical properties, but also understand its mechanism of effect of driving pile from microcosmic viewpoint. It further provides guidance to the practice. To obtain the microstructural and mechanical parameters, microstructural tests and consolidated undrained triaxial tests were carried out respectively. In addition, the soil specimens of different sites around the piles were obtained at different times during pile driven according the actual engineering in Tianjin's Binhai New Area. Through analysis of the representative components, three representative components were extract to describe the microstructural characteristics of the squeezed soil.The paper has the following findings. The three representative components have a good corresponding relationship with the soil cohesive strength and a weaker association with the soil internal friction angle. The first representative component contains nearly all the information. The second and third representative components make further additions to those properties that cannot be extracted from the first representative component. Besides, analysis shows that the soil microstructural properties control the strength character. There is an inverse relationship on the macro mechanical property between the soil near ground surface and the lower soil layers during pile driving. These results provide strong supports to the argument that the microstuctural parameters are the crucial factors of mechanical character by the representative component analysis.