Abstract: The techniques of correlation analysis and principal component analysis are introduced into the field of microstructural study.The means of correlation analysis and principal component analysis on the parameters of soil microstructure are put forward successively.These means can be utilized to eliminate the superposition messages obtained from different parameters of microstructure and to reduce the dimension of parameter matrix for microstructure markedly.The minority representative principal components can approximately synthesize the overall meaning of microstructure according to the desired value of accumulative contribution,which makes possible the extensive use of microstructural theory in soil mechanics.The deduced principal components can be used to establish constitutive equations,strength criteria and other theories in soil mechanics to mirror relationships between microstructure and macroscopic mechanical variables.Studies on a swatch composed by 64 clay SEM photos display that the message superposition is clear and severe among microstructural parameters.The first and the second principal components deduced,whose accumulative contribution is 95.28%,can exhibit almost all messages expressed by the 6 original microstructure parameters.The proposed method can be employed to establish the principal components for any kind of soil even it is illustrated by the given clay samples.