An optimization device and method for a casting blank production plan during a period of rapidly exchanging a tundish belongs to the field of automatic control of continuous casting. The length of an intermediate blank is adjusted into the sum of the length of a fixed size blank length, a blank head setting length and a blank tail setting length through optimizing the casting blank production plan before a joint point is optimized; when the optimization device is used for linearly cutting, only the blank head setting length and the blank tail setting length are cut off, and a residual casting blank is still a casting blank product without quality problems. The device is composed of industrial equipment and a software processing unit; the industrial equipment comprises a server and an industrial computer; the software processing unit comprises a data communication unit, a data storage unit, a production plan optimization calculation unit and a client. The optimization device and method have the advantages that waste blanks are reduced with regard to cutting optimization treatment of the tundish produced during the period of rapidly exchanging the tundish, the yield of liquid steel is improved and the production cost is reduced.