The invention belongs to the technical field of cold-rolled strip steels and discloses a control method for a ductility fluctuation of a temper mill. The control method comprises the following steps: obtaining a strip steel speed at an inlet of the temper mill and a strip steel speed at an outlet of the temper mill to obtain an actual ductility of the strip steel; obtaining a first ductility deviation value according to the actual ductility of the strip steel and a set ductility set of the strip steel; obtaining a rolling force correction value from the first ductility deviation value through a ductility proportional-integral controller; and obtaining a second ductility deviation value according to the rolling force correction value. The control method is capable of improving the ductility control accuracy at low-speed and acceleration/deceleration stages, and meanwhile, ensuring the ductility control accuracy at a high-speed stage and reducing a ductility deviation section length of each of the head and the tail of the strip steel.