In this work, a novel melamine-formaldehyde-Fe3O4 foam was prepared from a mixture containing melamine-ethanolamine-formaldehyde resin, melamine-glycol-formaldehyde resin and carboxylated Fe3O4 nanoparticles by microwave foaming method. The two resins were characterized by C-13-NMR, respectively. The structures of foams, mechanical and fire-retardant properties were experimentally characterized separately by scanning electron microscopy, universal testing machine, limit oxygen index, thermogravimetry-differential thermal analysis, and Fourier transform infrared spectra. The effects of the resin viscosity, emulsifier, nucleating agent, curing agent, silicone oil, microwave heating time and blowing agent on the structure of foam were investigated. Results showed that the properties of foam were decided by not only the molecular structure but also structure of foam, and the carboxylated Fe3O4 nanoparticles can improve the toughness and flame retardant properties of magnetic foam obviously from both aspects. (c) 2013 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 130: 2688-2697, 2013