This paper proposes a bionical working principle of a new rotary actuator. Based on this principle,its structure and controller are designed. The stator of the acturator has the shape of a cylinder;Its rotator has the shape of a lantern,which is composed of piezoelectrical elements(PZT)and circular notched mechanism. The controller includes current loop,position loop,correcting loop, etc. It has many advantages such as high precision,wide stepping range(steplessly adjustable),inner sensor,perfect output characteristics and powerful ability to resist load interference.