Abstract: Laser-driven electrons can produce high-quality X-ray source with broad applications including measurement of shock-compressed matters, inertial confinement fusion and laboratory astrophysics. For high energy density experiments, bright high-resolution diagnosis radiation is required. To meet the requirement, it is decisive to optimize the production of hot electrons and radiation emission. In this paper, we combine the Particle-In-Cell and Monte Carlo simulation, firstly use near-critical-density plasma to accelerate high-charge energetic electrons (exceeds 600 nC, 15 MeV) by direct laser acceleration in self-focusing channel, then get enhanced energy conversion between electrons and photons, finally obtain brilliant micro-spot (FWHM200 m) high-energy X-rays via parameter optimization. Our findings provide a promising access to high-spatial-resolution (200 m) diagnostics, and it is hopeful to realize single-pulse transient imaging based on laser-plasma bremsstrahlung source.