Law as language is the product of a particular culture and society. In socio-linguistic context, language represents an essential element of the human personality which has a deep effect on identity and dignity and the way to use a language. A semiotic approach is designed to uncover the basic structural elements of the meaning of a term and emphasises that the relation between signifier and signified is subject to dynamic change. Legal semiotics aims to develop a unified principle of intelligibility regarding all aspects of the legal phenomenon. 'De facto marriage' as a legal term was implicitly mentioned as the Marriage Law of the Chinese Soviet Republic stipulates: 'When a man and a woman cohabit, whether registered or not, it is taken as marriage'. In the several opinions on dealing with cases involving cohabitation in the name of the husband and wife without registration issued in 1989 by the supreme people's court explicitly proposed the concept of 'illegal cohabitation'.