Reactive blending of polyamide 6 (PA) with polyethylene (PE) having reactive site, maleic anhydride (MAH), and PE having glycidyl methacrylate (GMA) units was carried out using a gram-scale mixer at 240 degreesC. Morphology of reactive blend was studied by light scattering and transmission electron microscopy (TEM). TEM observation revealed that Y-shape PA-PE graft copolymers in situ-formed in PE-rich system, 30/70 PA/PE wt ratio, were easily pulled out from the interface and the copolymer micelles were dispersed in PE matrix when PA chain was short (IPA; M-w = 29k). It implies that the copolymers cannot act as an emulsifier for particle size reduction. Actually, light scattering analysis showed that the size reduction during melt mixing was a slow process. When PA chain was long (hPA; M-w. = 47k), the pull-out of in situ-formed copolymers hardly occurred, and the average PA particle size quickly decreased during melt blending, implying a nice emulsifying effect of the copolymers. In PA-rich systems (65/35 PA/PE), the pull-out of inverse Y-shape graft copolymer took place only when PA chain was long. In a 40/601PA/PE-GMA blend, the pull-out of Y-shape graft copolymer took place to yield micelle formation in PE phase and phase inversion occurred to render a PA-matrix morphology when PE trunk chain was long. By contrast, neither the micelle formation nor the phase inversion took place in a short trunk PE chain system.