The invention belongs to the technical field of pneumatic servo, and in particular, relates to a pneumatic fixed corner servo motor. The pneumatic fixed corner servo motor comprises a first annular rail, an annular cylinder piston, a piston inclined port, a second end wall, a first annular rail support, a first circular plate, a second annular rail, a positioning spring, a second circular plate, a damper and the like, wherein when high-pressure gas instantly dashes into an annular cylinder, the annular cylinder piston can generate reciprocating vibration under coaction of gas pressure and the positioing spring, and the damper can stop the reciprocating vibration of the annular cylinder piston, so that the annular cylinder piston reaches one position to stop. When the annular cylinder has the high-pressure gas, a damping clamping plate mounted on a damper shell is immovable, and a damping slide piece mounted on a swing shaft rotates along with a swing shaft; and as a damping oil pipe is thinner, damping oil cannot be quickly drained from a damping oil outlet to a damping oil inlet to stop the reciprocating vibration of the annular cylinder piston, and the practical effect is higher.