The invention relates to a friction brake for locking cylindrical parts by four stop blocks. The friction brake comprises such parts as a base, stop block parts, a slide way mechanism, a wedge block mechanism, a driving rod and a driven rod. The driving rod, the driven rod and the slide way mechanism form an altered crank slide block mechanism; a hydraulic motor drives the driving rod to rotate through a coupling; and the driven rod is enabled to push the slide way mechanism to move in the vertical direction so as to drive the stop blocks to move up and down. Meanwhile, the stop blocks respectively finish the actions of braking and releasing under the effects of a conical surface of the base and a wedged part under the wedge block mechanism. When the stop blocks lock a brake rod in a lowest point, a pressure angle on the driven rod is 90 degrees, and the slide way mechanism and the stop blocks are self-locked. The friction brake is compact in structure, smaller in weight and size and easy to arrange, can realize mechanical self-locking in the locking position, is high in braking reliability, can perform braking on whole cylindrical parts, is long in braking distance, and enables the axial braking performances of the cylindrical parts to become better.