The invention discloses a fastening mechanism used for installation of shelves. The fastening mechanism comprises two bodies fixedly connected with installation boards respectively; the two ends of each body comprise base parts with annular surfaces used for being combined with the back faces of supporting legs of the shelves and horizontal column parts which are integrally formed and perpendicular to the annular surfaces; each horizontal column part comprises a cylindrical inner side portion which is close to the corresponding installation board, integrally connected with the corresponding annular surface and used for being combined with a fixing hole of the supporting leg of the corresponding shelf, a cylindrical outer side portion located away from the tail end of the corresponding installation board, and a middle extending portion which is located between the cylindrical inner side portion and the cylindrical outer side portion and is cylindrical on the whole. The fastening mechanism used for installation of the shelves can also control alternate mounting and dismounting of two shelves simultaneously, when one shelf is mounted, the other shelf can be dismounted at the same time for special needs, and therefore the mounting and dismounting efficiency of the supporting legs of the shelves is improved and manual intervention is reduced.