A mechanism for locking and cushioning a spindle of a power tool includes a driving disk, a combination of a cam and a plurality of elastic components, and a plurality of roller pairs. The combination of the cam and the elastic components is accommodated in a body. The driving disk is disposed at one end of the body and in contact with the cam. A surface of the driving disk is formed with a plurality of stopping blocks inserted into the body to contact the elastic components, respectively. The roller pairs are respectively disposed between two adjacent stopping blocks and in contact with an inclined surface of an outer surface of the cam. When the power tool is powered off, relative movements between the elastic components and the stopping blocks and pressing forces between the inclined surface of the cam and the roller can cushion and lock the spindle.