In this article, polymer blends of polylactide (PLA) and co-polyester (co-PET) were prepared at various weight ratios of PLA/co-PET, such as 10/90, 20/80, 30/70, and 40/60, through a twin-screw extruder. The PLA nanofibers were fabricated by removal of the co-PET matrix in water at 80 degrees C. The morphology development of PLA dispersed phase obtained from the three different sample connections and the die of the twin-screw extruder were investigated by Scanning Electron Microscopy (SEM). It was found that the uniformed PLA nanofibers with averaged diameters less than 500 nm were fabricated by the suitable processing parameters. The processing immiscibility and rheological behavior of PLA/co-PET blends were also studied by means of Differential Scanning Calorimeter (DSC) and Capillary Rheometer. The test of Fourier Transform Infrared spectroscopy (FTIR) demonstrated that the co-PET was removed clearly in water at 80 degrees C. (c) 2013 Wiley Periodicals, Inc.