In this paper, we introduce the concept of Gorenstein flat comodules and give a description of colocalization of Gorenstein flat comodules. A right C-comodule M is called a Gorenstein flat comodule if there exists an exact sequence ... -> F-1 -> F-0 -> F-0 -> F-1 -> center dot center dot center dot of flat comodules with M similar or equal to Ker(F-0 -> F-1) and such that Com(C)(-, I) leaves the sequence exact whenever I is a finite-dimensional right C-comodule and id(C)( I) < infinity. Some properties of Gorenstein flat comodules are studied.