The invention discloses an actuator replacement mechanism of a radio telescope. The actuator replacement mechanism comprises a left pull rod assembly and a right pull rod assembly, the upper ends of the pull rod assemblies are connected with upper connecting rods and connected with lower stay cables via the upper connecting rods, the lower ends of the pull rod assemblies are connected with hydraulic cylinders respectively, and the hydraulic cylinders are connected with an actuator base. The pull rod assemblies are provided with sleeves, telescopic rods are arranged in the sleeves, the upper ends of the telescopic rods are connected with the upper connecting rods, the bodies of the telescopic rods are provided with a plurality of annular grooves circumferentially, and two locking mechanisms are oppositely arranged on outer sleeves of the sleeves, extend into the sleeves from shear keys and are matched with the annular grooves of the telescopic rods so as to limit the telescopic rods. The locking mechanisms are provided with flexible shafts to telescopically control the shear keys, and control handles of the flexible shafts are arranged near the lower ends of the sleeves.