The fabrication of polymer optical fiber coupler needed thermal pre-elongated taper on the partwhich would be twirled. When gravity pulled vertically fused elongated taper, the influence of polymer optical fiber characteristic in the different temperature and different stretch strength was studied. It is found when the heating zone center tem- perature is about 214℃ and the stretch strength is about 1. 40g, the process of the PMMA polymer optical fiber stretches is easy to be controlled and the PMMA POF has good op ticsquality.