Poly(2,6-dimethyl-1,4-phenylene oxide)/polyamide 6 (PPO/PA6) blends were reactively compatibilized by maleic anhydride (MA) grafted PPO (PPO-g-MA) and reinforced by short glass fibers (SGF) via melt extrusion. An observation of the SGF-polymer interface by scanning electronic microscope (SEM) together with etching techniques indicated that the PPO-g-MA played a decisive role in the adhesion of polymers to SGF. The rheological behavior was investigated by capillary rheometer, and the addition of PPO-g-MA, and SGF could increase the viscosity of the PPO/PA6 blends. The analysis of fiber orientation and distribution in the PPO/PA6/SGF composites showed PPO-g-MA favored to the random dispersion of SGF. The statistic analysis of SGF length showed that PPO-g-MA was helpful to maintain the fiber length during melt-processing. For the composites at a given SGF content of 30 wt %, the addition of PPO-g-MA increased the tensile strength from 59.4 MPa to 97.1 MPa and increased SGF efficiency factor from 0.028 to 0.132. The experimental data were consistent with the theoretical predictions of the extension of Kelly-Tyson model for tensile strength. The fracture toughness of the composites was investigated by single edge notch three-point bending test. (C) 2009 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 47: 2188-2197, 2009