After a short presentation of the Pluto-Charon system and the history of its mass determinations some first reasons are presented that support the existence of a ring of billions of small satellites about Pluto up to tenths of millions of kilometers. The stability, the shape and the dimensions of such an heavy ring are discussed. Finally a general review of advantages and drawbacks of this ring theory is presented as well as the possibilities of detection of the eventual Pluto's ring.