In this study, polyamide-66/poly(2,6-dimethyl-1,4-phenylene oxide) (PA66/PPO) blends with high viscosity ratio were processed by a self-designed triangle-arrayed triple-screw extruder (TTSE, which simulates extensional flow) and a commercial twin-screw extruder (TSE), respectively. Furthermore, in order to improve the mechanical properties of the immiscible PA66/PPO blends, PPO-grafted maleic anhydride (PPO-g-MA) and styrene-ethylene-butylene-styrene (SEBS) block copolymer were used. The mechanical properties, phase morphology, and rheological properties of both binary PA66/PPO blends and toughened PA66/PPO/PPO-g-MA blends were comprehensively investigated to compare the above mentioned two processing method. Samples processed with TTSE exhibited better mechanical properties than the TSE-processed blends. The morphologies of the blends were examined by scanning electron microscopy, exhibiting smaller particles sizes and narrower particle size distributions, which were attributed to the significant effects of extensional flow in TTSE. The toughening mechanism of compatibilized blends was investigated through morphology analysis, dynamic mechanical, and rhelogical analysis. Thus, TTSE with an extensional effect was proved to be efficient in the blending of high viscosity ratio polymers. (C) 2016 Society of Plastics Engineers