The invention discloses a novel power-driven protective cover for primary mirror of large aperture telescope, and belongs to the field of lens covering device installed on optical telescope. Aiming to solve the problems that the present protective cover has large wind resistance and poor operational stability, the protective cover of the invention is composed of four units, wherein each unit comprises a substrate, a cover plate, sealing strips, a linear actuator, an adjustable pull rod, a spherical headed joint, hinge struts and hinges. The sealing strips are arranged on linear edges of any two opposite covering plates, reinforcing ribs are riveted on the covering plates, the spherical headed joints are fixedly connected on vertical bars of the reinforcing ribs, the spherical headed joints are in connection with the adjustable pull rods, an ends of the hinge struts are fixedly connected on transverse bars of the reinforcing ribs, another ends of the hinge struts are connected with the hinges that are fixedly connected on the substrates, and the linear actuator is fixed on the substrates. The four covering plates rotate at 90 degrees, thereby positioning the four covering plates on a same plane and forming a round. According to the invention, the structure is simple, the weight is light, modular design is adopted by each unit, the interchangeability is strong, the assembly and disassembly operation are convenient, and the appearance is nice.