The recent advancement of high-intensity lasers has made all-optical Compton scattering become a promising way to produce ultrashort brilliant γ-rays in an ultra-compact system. However, so far achieved Compton γ-ray sources are limited by low conversion efficiency and spectral intensity. Here we present a highly efficient gamma photon emitter obtained by irradiating a high-intensity laser pulse on a miniature plasma device consisting of a plasma lens and a plasma mirror. This concept exploits strong spatiotemporal laser-shaping process and high-charge electron acceleration process in the plasma lens, as well as an efficient nonlinear Compton scattering process enabled by the plasma mirror. Our full three-dimensional particle-in-cell simulations demonstrate that in this novel scheme, brilliant γ-rays with very high conversion efficiency (higher than 10−2) and spectral intensity (∼109 photons 0.1 % BW ) can be achieved by employing currently available petawatt-class lasers with intensity of 1021 W cm−2. Such efficient and intense γ-ray sources would find applications in wide-ranging areas.