A pneumatic amplifier includes a valve body, a first comparison chamber, a third comparison chamber and a second comparison chamber. A first diaphragm and a second diaphragm are arranged in the first comparison chamber and fixed to the valve body. A mounting plate A is fixedly arranged between the first diaphragm and the second diaphragm. A seventh diaphragm, an eighth diaphragm, a ninth diaphragm and a tenth diaphragm are arranged in the second comparison chamber and fixedly arranged on the valve body. A mounting plate C is fixedly arranged among the seventh diaphragm, the eighth diaphragm, the ninth diaphragm and the tenth diaphragm. A third diaphragm, a fourth diaphragm, a fifth diaphragm and a sixth diaphragm are arranged in the third comparison chamber and fixed to the valve body. A mounting plate B is fixedly arranged among the third diaphragm, the fourth diaphragm, the fifth diaphragm and the sixth diaphragm.