[en] In this paper, we propose a robust and novel scheme to generate ultra-bright circularly polarized harmonics using non-collinear double-circularly polarized laser pulses irradiating over-dense plasma surface. Numerous advantages are demonstrated by three-dimensional particle-in-cell simulations including high efficiency of harmonic generation, the separation of the harmonics from the pump beams, the production of both left and right-circularly polarized harmonics at the same wavelength and the capability of separating the harmonics without a spectrometer. Relativistically oscillating mirror model (ROM) is adopted to explain the harmonic generation mechanism and a set of novel selection rules for our HHG technique is derived, which is consistent with the simulation results.