Creole is one of the main topics in the fields concerning the language change and evolution, such as sociolinguistics, the developmental psychology of language and so on. Our purpose in this paper is to develop an evolutionary theory of language to study the emergence of creole. We discuss how the emergence of creole is dealt with regard to population dynamics. We modify the language dynamics equations by Komarova et al., so as to include the generation parameter ‘ t ’. From the viewpoint of the population dynamics, we give the definition of creole as a language, which is predefined by the universal grammar together with pre-existing languages. We show experimental results, in which we could observe the emergence of creole. Furthermore, we analyze the condition of creolization in terms of similarity among languages.