We proposed a new method to yield brilliant keV–MeV x-ray emission, inspired by Cao et al (2010 Phys. Plasma17 043103). When a short femtosecond pulse is coupling into a microwire array target, due to the weakly unbalanced quasi-static electric and magnetic fields, the energetic electrons accelerated by the laser will emit a large amount of photons per shot, comparable to that from the laser-wake betatron radiation. It was found that the critical energy of the photons and the total photon yields are strongly dependent on the laser intensity and structure parameters of the target. The peak spectral brightness of the radiation in our scheme was estimated to be 4 × 1019 at the laser intensity 3 × 1020 W cm−2. More important, the photon energies can be extended to hundreds of keV to MeV readily if electron beam accelerated by the laser is in the range of MeV to GeV.