The invention relates to '8'-shaped PET / PTT hollow fiber and a process for preparation. The fiber is prepared by composite spinning which is obtained through melting polyethylene glycol terephthalate PET and polyytrimethylene terephthalate PTT slice. The process for preparation comprises drying PET and PTT polyester slice, entering into a composite spinning assembly through a twin-screw extruder in parallel, carrying out melt spinning, cooling through cross air blow, oiling on an oil tanker, drafting by two channels, coiling, finally obtaining '8'-shaped PET / PTT hollow fiber. The fiber fully exerts the excellent property of PTT and PET fiber, which is thermal insulating, highly moisture absorbable and breathable, soft and touching, since PTT and PET fiber have different shrinkage ratio and have the potential function of coiling property, the product has greatly wide application prospect in the field of clothing face fabric and various filling material.