The invention relates to a hot continuous rolling variable target straightness control method based on Smith pre-estimation control. The straightness control method comprises the following steps of firstly, issuing straightness target values of different positions of strip steel according to steel types; carrying out roll bending force setting on the finish rolling tail mill frame; tracking the length of the strip steel in real time after the tail mill frame is detected to bite steel; and performing variable target straightness feedback control based on Smith pre-estimation control after the strip steel is detected by a straightness instrument and is delayed for a period of time. According to the method, the variable target straightness control is carried out on the finish rolling strip steel, the control requirements of some special steel types on the straightness of the strip steel are met, the problem that an existing control method cannot meet rapid and stable target control with large straightness is solved.