A series of polyimide composites reinforced with different loadings of silicon carbide (SiC) nanoparticles are prepared by in-situ polymerization technique. The polyimide (PI) matrix resin is derived from 4,4'-oxydianiline (4,4'-ODA) and pyromellitic dianhydride (PMDA). The dispersions of SiC nanoparticles are prepared via ultrasonic irradiation or mechanical homogenization. In this method, the SiC nanoparticles are dispersed in diamine solution followed by polymerization with dianhydride. The composites obtained under sonication were found to have lower thermal properties than composites prepared under homogenization.