The invention discloses an inner-cavity sand blaster for circuit breaker shell processing adopting a bidirectional pneumatic principle. The inner-cavity sand blaster for circuit breaker shell processing adopting the bidirectional pneumatic principle structurally comprises a telescopic pressing plate, a workpiece tray, positioning holes, a positioning base and a connecting rod, wherein the four positioning holes are formed in four ends of the positioning base through a penetrating way; and the middle part of the surface of the positioning base is fastened with the bottom part of the connectingrod. According to the inner-cavity sand blaster for circuit breaker shell processing adopting the bidirectional pneumatic principle provided by the invention, a workpiece to be sand-blasted is placedon the workpiece tray and is pressed and positioned through the telescopic pressing plate; when the direction and the angle of the workpiece need to be switched, a sand blasting air gun can be used for blowing a bidirectional driver so as to drive a built-in conversion device to rotate, and during the rotation process, an ejector switches the direction, and an ejection position is changed synchronously, so that the angle and direction switching during the workpiece sand blasting process can be accomplished; and in addition, once if the workpiece is fixed, no hand operation is needed, so that hands of working personnel can be effectively prevented from being impacted by the sand blasting gun, and burrs can be removed cleanly.