The present application discloses a dual-rail motion focusing radiotherapy device, comprising a fixed rack and a rotary rack. The fixed rack is provided with a ring sleeve structural member; the rotary rack is provided with an annular structural member and a supporting structural member; the annular structural member is connected to the supporting structural member; the annular structural member is located on the inner side of the ring sleeve structural member and is connected to the ring sleeve structural member by means of bearings; the annular structural member and the ring sleeve structural member are connected to a rotation driving apparatus, and the rotation driving apparatus drives the annular structural member to rotate along the ring sleeve structural member; a treatment assembly and an imaging component are mounted on the supporting structural member; a drive mechanism is mounted on the supporting structural member and can drive the treatment assembly to slide. By integrating the imaging component and the treatment assembly, the device improves the accuracy of image guidance and target point positioning, shortens the time of radiotherapy, and reduces the damage to normal tissue and organ cell of a patient by means of dual-rail focusing, such that a treatment solution can be more optimized.