A kind of cable-driven pneumatic flexible manipulator for apple passive grasp was designed to satisfy the requirements of packaging production lines in sorting different sizes of apples. The objective function was determined by the minimum change range of apple grasp strength. Matlab software fmincon function was applied to optimize the function. Two structure sizes a and δ, the stiffness of hydropneumatic twist spring k, preloaded angle -10, and the angle for grasping the smallest apples -2 were resolved. The initial state of manipulator and pneumatic control method was put forward.