Abstract: The stratificational nature of language as sign is a core concern of modern linguistics. Although Saussure himself did not study the stratificational nature of linguistic sign， his philosophical understanding of the two binary opposites—signifier vs. signified， form vs. substance， arbitrariness of the sign and linear character of the signal， provides a common theoretical background for Hjelmslev， Lamb and Halliday to develop their stratificational theories. Based on a careful comparison and contrast of how the strata are classified， what each stratum consists of and what the relationships among and within the strata are， this paper describes and comments on the background and development of the three linguists stratificational theories in order to have a better understanding of the properties of linguistic sign.

Key words: theory of linguistic stratification, Saussure, Hjelmslev, Lamb, Halliday