The invention relates to the field of elevators, in particular to a design method of a brake unit of an elevator, and discloses a design method of the elevator. The elevator mainly comprises a bracket and guide rails, wherein the bracket is fixedly connected with a car, and the guide rails are arranged along an elevator shaft. The design method is characterized in that a triggering unit is arranged on the bracket, rollers and first gears are freely and rotationally arranged on the bracket through support shafts, each guide rail is arranged between the corresponding first gear and the corresponding roller, each first gear is engaged with a toothed surface of the corresponding guide rail, each roller is in rolling fit with the polished surface of the corresponding guide rail, second gears rotate around each first gear through a connecting rod, are engaged with the corresponding first gear, and are respectively arranged at the upper side and the lower side of the corresponding first gear, and a triggering hole is formed in each connecting rod and is in inserting fit with the triggering end of the triggering unit. The design method has the advantage that when the triggering end is removed out of the corresponding triggering hole, the second gears are engaged with the guide rails under the action of elastic force of elastic restoring parts, the degree of freedom of the mechanism is 0, and the elevator cannot run up and down, so as to brake the elevator under the fault condition.