The present invention is to provide a mechanism for fastening a rear side of computer comprising a rear panel provided at the rear of a case of the computer, and a fastening assembly having one end pivotably connected to the case adjacent the rear panel for pivoting the fastening assembly to approach or move away from the rear panel, wherein, after a plurality of fastening members being mounted at the rear panel, the fastening assembly is able to tightly press the fastening members thereby sandwiching an engagement piece of each fastening member between the fastening assembly and the rear panel and quickly fastening the fastening members at the rear panel.