The invention relates to a finishing device for producing a magnesium alloy rolled plate, which is suitable for the field of metallurgical machinery application. The finishing device sequentially comprises a conveying rail, a straightening machine, a conveying rail, a throwing machine, a No.1 three-sand-frame double-sided sander, a plate moving machine, a conveying rail, a conveying rail, a hot-air stirring resistance heating furnace, a heat plate wiper, a No.3 three-sand-frame double-sided sander, a No.2 three-sand-frame double-sided sander, a conveying rail, a conveying rail and a plate moving machine, wherein the straightening machine is mounted between the conveying rails; the throwing machine is connected to two lateral plates of the No.1 three-sand-frame double-sided sander and thenis mounted between the conveying rails; the plate moving machine is mounted between the conveying rails; and the No.3 three-sand-frame double-sided sander is integrally connected with the heat plate wiper and the lateral plate of the hot-air stirring resistance heating furnace and then is fixed along an exit direction of the conveying rail. The finishing device can be used for promoting the yieldof the cold-rolled magnesium alloy rolled plate, reducing the production cost and producing a wide and thin magnesium alloy plate strip.