A parallel bi-level image sharpening methodology in Compute Unified Device Architecture (CUDA) circumstance was proposed especially for the improvements on fuzzy boundaries and poor quality when enlarging low resolution photos or images. A GPU-based parallel sharpening algorithm with two stages was designed and implemented. Firstly, the parallel linear interpolation algorism was repeatedly adopted by the calculation of non-edge region and the sharpening treatments of edge area. Secondly, an improved gradient method was utilized for the further optimized images. The jagged edges of the enlarged images were basically eliminated by the proposed method, making the images much more smooth, natural, and legible. The experimental results prove that the GPU-based parallel image sharpening algorithm is superior to the currently popular algorithms in calculation efficiency and image quality, and it can be applied in sharpening images and amplifying photos.