Abstract: With 4,4'-diamino diphenyl methane (DDM) as the curing agent, bismaleimide (BMI) and phenolic epoxy resin (F51) as the matrix, polyethersulfone (PES) as the toughening agent and functionalized nano SiO₂ by silane coupling agent KH560(KH-SiO₂) as the modifier, the KH-SiO₂-PES/BMI-F51 composites were prepared by in-situ polymerization method, and the curing process and reaction curing kinetics were determined by non-isothermal DSC. The apparent activation energy of KH-SiO₂-PES/BMI-F51 composites are 96.03 kJ/mol and 99.18 kJ/mol according to Kissinger equation and Ozawa equation, respectively. The FTIR results reveal that the surface modification of KH-SiO₂ is favourable, the characteristic peaks of unsaturated double bond and epoxy group disappear, and the C=C double bond in BMI and epoxy group in F51 are involved in the curing reaction of KH-SiO₂-PES/BMI-F51 composites under the effect of DDM. The SEM images exhibit that PES resin and KH-SiO₂ uniformly disperse in the resin matrix when the content of PES resin and KH-SiO₂ are appropriate, the broken cracks develop irregularly and the material exhibits ductile fracture. The mechanical performances and thermogravimetric properties show that bending strength, bending modulus and impact strength of KH-SiO₂-PES/BMI-F51composites are 156.23 MPa, 4.18 GPa and 20.89 kJ/m², when the mass fraction of PES and KH-SiO₂ are 4wt% and 1.5wt%, which are 49.7%, 29.4% and 82.8% higher than that of BMI-F51 matrix, respectively. The thermal decomposition temperature of KH-SiO₂-PES/BMI-F51 composites is 393.1℃, and the temperature at the residual mass of 50% reaches 523.1℃, the heat-resistant property is excellent. The mechanical properties and heat-resistant properties of KH-SiO₂-PES/BMI-F51 composites are greatly improved, which provides theoretical data for expanding the application range of F51 and BMI.