Abstract: Silicone resin was modified with polymer of methyldiphenylaeetylenesilane(PSP). The curing mechanism，heat resistance and mechanical properties of silicone resin and its composites were studied by FTIR and TGA. Results show that when the mass ratio of HS to PSP is 5∶5,the temperature of 5% mass loss (Td5) of the cured blends is 691 °C, residual of mass is 88％ based on the initial mass at 1 000 °C in nitrogen. The impact strength is 21 kJ/m2, the flexural strength is 65 MPa, the retention rate of flexural strength is 78% at 200 °C, the dielectric constant is 4.6, the dielectric loss factor is 7.9×10-3 and the insulation resistance is 6.7×1013 Ω. Composites have excellent properties of mechanics, high temperatureresistance and dielectric.