Using methacrylic acid (MAA), acrylonitrile (AN), and acryl amide (AM) as monomers, a new high-performance PMI copolymer foam was prepared via radical bulk copolymerization and free heat foaming; afterward, the effects of photo initiation polymerization technology on the foam mechanical and craft performances were further researched. The results showed that photo initiation technology was only fit to be used as the prepolymerization reaction during the preparation of PMI copolymer foam, and it was faster and more easily controlled than thermal initiation prepolymerization. Photo initiation prepolymerization could eliminate not only the foam inner flaws, but also the size nonuniformity of the foam cells effectively. Accordingly, photo initiation prepolymerization is able to make the foam uniform, transparent, stable, and isotropy, and moreover improve the foam tensile strength. (c) 2009 Wiley Periodicals, Inc. J Appl Polym Sci 112: 3041-3047, 2009