Abstract: The cure temperature of bismaleimide (BMI) resins is known to be higher than 200℃, although their heat resistance and many other properties are excellent. The authors previous study¹ has shown that initiator is very effective in lowering the cure temperature of BMI resins, but its cured resin is brittle. This paper tried to use diamine extender and diallyl bisphenol A comonomer to increase to ughness of modified resin. An optimum resin form ulation cured at 150℃ was obtained using a computer-aided quadratic regression orthogonal combination design method. The resin casts have been detected to have the properties of middle toughness and excellent heat resistance, and composites to have good mechanical properties. This work has laid a good foundation for manufacturing composite tools and structures.