A novel approach of in situ polymerization and in situ compatibilization was adopted to prepare poly(2,6-dimethyl-1,4-phenylene oxide) (PPO) and polyamide 6 (PA6) nanoblends. Anionic ring-opening polymerization of epsilon-caprolactam was carried out in the presence of PPO, the chain of which bore p-methoxypenylpropionate (MPAA), acting as macroactivator to initiate PA6 chain growth from the PPO chain and form a graft copolymer of PPO and PA6 and pure PA6 simultaneously. The nanostructured PA6 dispersed phase in the PPO matrix could be achieved.