The novel technical scheme of oval supercavity is presented. The light intensity in focus of oval supercavity are computed. By using the Compton scattering theory, the high brightness laser synchrotron source based on the technique of oval supercavity, including photon yield and radiant power, are calculated and discussed. The results show that when the reflectivity of oval supercavity mirror is equal to 99.99%, the light intensity in focus of oval supercavity is about 5000 times higher than that of the incident intensity （I0）. the γ-ray with energy up to 10975 MeV are expected to be produced by Compton vertical scattering of laser photons on the 3.5 GeV electron bunches, the photon yield and the radiant power of Compton vertical scattering between electron bunches and laser beam in focus of oval supercavity is about 25×107 times higher than that of Compton vertical scattering between electron bunches and single laser beam.