Abstract: Bismaleimides are being increasingly used as matrix resins for advanced composites.There are some ploblems,however,such as the brittleness of this kind of polymers due to the high crosslink density in network polymgrs.In this article,the recent advancement of modified bismaleimide resin systems with improved toughness as matrix for composites is summarized.The chemical methods for toughening bismaleimide such as rubber toughening of bismaleimide,copolymerizing it with allylphenyl compounds Michael addition chain extention,taking thermoplastics as toughening modifiers,using bismaleimide-modified epoxy resins and synthesizing chain-extended bismaleimides are reviewed.