This study's objective is to analyse a variety of functions and uses of se in Spanish system. Se, a Spanish reflexive pronoun, which comes from the accusative of the Latin reflexive pronoun of the third person sē, plays diverse roles in Spanish grammar and has many meanings. Reflexive verbs, transitive verbs accompanied by a reflexive pronoun, indicate that the subject acts on itself. Almost all of the human languages may have their own reflexive pronoun like se. This research on se is thought to contribute not only to our knowledge about its important syntactic structures, but also to the solution of various communication problems, caused on account of subtle differences of its meaning. This study consists of three chapters, an introduction and a conclusion. The first part of those chapters, 'reflexive pronoun < se >', in its turn, is divided into three sections : 'se in reflexive sentences' (Juan se sienta en la silla del director), 'se in quasi-reflexive sentences' (Juan se ira de Madrid el 5 de mayo), and 'pronominal verbs' (se arrepintio de sus actos). And we will investigate different uses of se by dividing the second chapter, 'grammatical sign < se >', into three sections: 'impersonal sign se' (se trabaja poco aqui), 'passive sign se' (se vendieron los coches), and 'interpretation of the dative in passive sentences with se' (se nos averio el coche). The third chapter, meanwhile, is essential in providing analysis of functions and uses of reflexive pronoun of the Latin, the Italian, and the French, and also we try to explain them in comparison with those of the Spanish se.