Abstract: In this paper we give the following results:(1)Every group is a syntactic monoid of language X^* with X being a maximal strong code; (2) Recognizable strong code X can decompose into two recognizable strong codes iff there is a proper congruence in the minimal automaton recongnizing X^*; (3)the maximal strong code, whose syntactic monoid is a simple group, is called a simple maximal strong code. Any recognizable strong code can decompose into a finite number of simple recognizable strong codes.

Key words: composition of codes, simple group, recognizable code, automaton, strong code