Abstract: The present invention relates to a cylinder-operated driving mechanism for a ball valve, and more particularly to a cylinder-operated driving mechanism for a ball valve in which a plurality of guided compression springs are loaded between the cylinder caps at two ends of the cylinder and the two horizontally opposite pistons of the cylinder such that when there is no air supplied to the cylinder for driving the closing of the ball valve, the compressed spring force stored in the guided compression springs can push the two pistons to move toward each other and thereby turn the driving shaft connected to the pistons via links and driving shaft seat and further stably and reliably drives the ball valve to turn close.