The invention provides an LDP Sn medium EUV light source system realized by adopting a magnetic dragging structure and relates to an extreme ultraviolet photoetching light source technology, aiming at solving the problem that an Sn target dragging device of an LDP EUV light source cannot ensure that a Sn target and the outside are located at a vacuum isolation state. A Sn target dragging device provided by the invention is realized by adopting the magnetic dragging structure; a rotary motor in the magnetic dragging structure is used for driving an electromagnet to rotate; the electromagnet drives a Sn target to rotate and the Sn target is round and can rotate around the axis; a supporting frame is a round framework with an electromagnet; the Sn target is fixed on the supporting frame; the supporting frame is located in a vacuum discharging chamber of the LDP Sn medium EUV light source system; and the rotary motor and the electromagnet are located outside the vacuum discharging chamber of the LDP Sn medium EUV light source system. The vacuum isolation of the dragging structure, a power supply and the Sn target can be realized, the structure is simple and the control precision is high; and the technical scheme provided by the invention is applicable to the LDP Sn medium EUV light source system.