The utility model discloses a baking oven door lifting device used for testing the thermal shrinkage rate of a guy wire. The baking oven door lifting device is characterized in that a baking oven body (1) is provided with a guide rail (2) and an air cylinder (8), and a baking oven door (3) is arranged on the guide rail (2) and can ascend and descend along the guide rail (2); the baking oven door (3) is connected with an air cylinder rod (9) of the air cylinder (8) through a connecting wire (5); the connecting wire (5) bypasses a roller wheel (6) installed on a roller wheel support (7), the stressing direction of the connecting wire (5) is changed, and the roller wheel support (7) is fixed at one end of the top of the baking oven body (1) through screws; and the air cylinder (8) is horizontally arranged at the top of the baking oven body (1) and is connected with an air source. According to the design, the baking oven door lifting device provided by the utility model is provided with automation equipment such as the air cylinder, the air cylinder is connected with the connecting wire so as to drive the baking oven door to move, so that the baking oven door can be opened and closed automatically, and thus the automatic measurement of the thermal shrinkage of the guy wire is realized.