The morphological evolution of thermoplastic poly (vinyl alcohol) (PVA) and Poly (lactic acid) (PLA) blend filaments along the spinline is investigated for the first time. Emphasis is placed on considering the elongation rate that influence the final state of deformation of the dispersed PLA phase. For the study, the PVA/PLA blend filaments at different locations along the spinline in melt spinning process are collected by using a special self-constructed fiber-capturing device. This fiber collecting device allows closer off-line study of the morphological properties of PVA/PLA blend filaments. The elongation rate at different zones along the spinline is calculated from displacement/velocity data that measured using Laser Dopplyer Velocimetry (LDV) technique. Experimental results indicate that the effect of elongation rate on the morphological evolution of the PLA dispersed phase in PVA/PLA 70/30 blend is significant: A higher elongation rate leads to smaller the PLA dispersed phases in size.