We improved the adhesion between silicon based insulating materials and epoxy resin composites by adding the adhesion promoter cycloborosiloxane (BSi, cyclo-1,3,3,5,7,7-hexaphenyl-1,5-diboro-3,7-disiloxane). The experimental results show that the addition of BSi in the silicone rubber (SR) system significantly increases the tensile shear strength between BSi and epoxy resin (EP), reaching 309% of the original value. On this basis, the mechanism of BSi to enhance the adhesion effect was discussed. The electron deficient B in BSi attracted the electron rich N and O in EP to enhance the chemical interaction, combined with the interfacial migration behavior in the curing process, to improve the adhesion strength. This study provides the design and synthesis ideas of adhesive aids, and a reference for further exploring the interface mechanism of epoxy resin matrix composites.