The invention discloses a pneumatic actuating mechanism for a one-way damping valve and belongs to the technical field of catalytic cracking units of the petrochemical industry. The pneumatic actuating mechanism for the one-way damping valve comprises a first air cylinder, a second air cylinder, a shifting fork shaft, a shifting fork and an air cylinder reversing control unit. The rod portion of the shifting fork is fixedly connected with a valve shaft of the one-way damping valve. The air cylinder reversing control unit is used for controlling reversing of the first air cylinder and the second air cylinder. The pneumatic actuating mechanism further comprises an engagement and disengagement mechanism which is a cylinder body. The engagement and disengagement mechanism is provided with a guide groove in the longitudinal length direction. The two ends of the engagement and disengagement mechanism are fixedly connected with a piston rod of the first air cylinder and a piston rod of the second air cylinder correspondingly. The shifting fork shaft extends into a U-shaped opening formed in the end of the shifting fork and the guide groove in the engagement and disengagement mechanism. The shifting fork shaft can slide in the U-shaped opening and can conduct linear motion in the guide groove at the same time. The pneumatic actuating mechanism can improve the energy efficiency, guarantees that the one-way damping valve is closed under an emergency condition and protects the seal face of the one-way damping valve at the same time.