The invention provides a power assembly suspension rear bracket and a power assembly suspension failure mechanism. The suspension rear bracket comprises a first component and a second component, wherein the first component comprises a lower plate, and a first end of the lower plate is bended to extend to a second end to form an upper plate; a first hole is formed in the upper plate, a second hole is formed in the lower plate, and the position of the first hole corresponds to that of the second hole; a first long groove is also formed in the lower plate; the second component comprises a plate part; a second long groove and a third hole are formed in the plate part; the plate part is located between the upper plate and the lower plate; a first fastening piece passes through the first hole, the second long groove and the second hole to be fixed; a second fastening piece passes through the third hole and the first long groove to be fixed, and is suitable for moving in the first long groove; and besides, the first fastening piece is suitable for moving in the second long groove, so that the second end of the lower plate is away from or close to the plate part. Through the adoption of the power assembly suspension rear bracket provided by the invention, when the front part of an automobile is collided, the power assembly suspension rear bracket is failed in the same failure manner; and the power assembly suspension rear bracket cannot be deformed or twisted.