Abstract: Differential scanning calorimetry was used to study the effect of the peroxide on the cure reaction of BMI. The effect of peroxide content on the properties of the cured BMI was investigated. The results show that the peroxide reduced the initial reaction temperature and prompted the reaction speed, increased the bending strength and decreases the impacting strength. So the peroxide content should be less than 0.6%. CF/SiO₂/BMI composites are fabricated from the BMI containing peroxide and its microstructure and properties are better than those of the composites free of peroxide. According to the injection molding experiment the spilling problem is overcome and the forming time is reduced from two hours to fifteen minutes when peroxide was added.