A fastening mechanism for detachable keyboard modules with the keyboard module consists of at least one fastening seat. The fastening seat engages with a fastening means. The keyboard module is fastened to a computer casing through the fastening means. The fastening means includes a body, two slide channels and an elastic element. The body has a second fastener located at the front end thereof and a housing chamber located at the rear end thereof. The two slide-channels are located at two sides of the body to form a slidable coupling with two slides which located at two sides of the fastening seat. The elastic element is restricted between the housing chamber and a stopping flange which located at a rear end of the fastening seat. The elastic force of the elastic element may push the fastening means forwards to enable a second fastener located at the front end of the body to engage with a first fastener located at the computer casing thereby to enable the keyboard module fastening to the computer casing. When the fastening means is moved rearwards, the second fastener is separated from the first fastener thereby enabling the keyboard module detached from the computer casing.