Polymer blends incorporating poly(ethylene terephthalate) (PET), polyamide-6 (PA-6), and a reactive compatibilizer (low molecular weight bisphenol-A epoxy resin-E-44) were prepared with the following E-44 weight percent concentrations: 0, 0.3, 0.6, 1, 3, 5, and 10. The samples was studied by a scanning electron microscope (SEM), a polarizing microscope (PLM), dynamic mechanical thermal analysis (DMTA), wide-angle X-ray diffraction (WAXD), a differential scanning calorimeter (DSC), infrared spectroscopy (IR), and mechanical testing. SEM and PLM showed noticeable changes in both the amorphous region and the crystalline region of the blends. The changes indicated better compatibility between the dispersed phase (PA-6) and the matrix (PET), which was further confirmed by the DMTA test. The WAXD showed that PET and PA-6 crystallized separately and no cocrystallite was found. The melting and crystallization data, obtained by DSC, suggested that the crystallization of the blend was blocked, although the hindered mechanism for the effect of E-44 on PET was different from that on PA-6. The notched impact strength and flexural strength of the PET/PA-6 blends were significantly improved when the content of E-44 was 5 wt % (improved about 500 and 400%, respectively). IR was used to study the reaction among E-44, PET, and PA-6. The result indicated that the grafting reaction and the crosslinking reaction occurred during melt blending. The obvious increase of mechanical properties and the reinforcing and toughening effect were attributed to the formation of the crosslinking net in the blend.