A novel direct volume reconstruction method based on reverse geometry for cone beam X-ray projections is presented. We combine the cone beam boundary reconstruction with reverse geometry by extending one or two detectors to many point-shaped detectors located purposively in 3D space. The boundary reconstruction algorithm and its numerical simulation on two volume phantoms have shown that the new reverse geometry is worth considering and exploiting compared to the conventional X-ray cone beam boundary reconstruction in case of X-ray projection noise.