The invention belongs to the technical field of pre-straightening and cooling in a steel rolling production, and provides an online accelerated cooling method with a function of pre-straightening. The method comprises the following steps of: delivering steel plates which are in a thickness range of 6 to 80 mm after carrying out a finish rolling to a pre-straightener to straighten through a conveying roller way; introducing the steel plates into an online accelerated cooling area and fast cooling a temperature from 700 to 950 DEG C to 450 to 700 DEG C, and introducing the steel plates to a heavy straightener to straighten after the temperature is uniform. The pre-straightener and an online accelerated cooling device are arranged continuously and tightly, so that the pre-straightening and the accelerated cooling are synchronous. In the accelerated cooling, the roller way is used for varying a deceleration and an acceleration, thereby solving the problem of the inhomogeneity caused by that a temperature difference between steel and plates is more than 40 DEG C. As the pre-straightening and the accelerated cooling are synchronous, a process flow is effectively reduced. Therefore, a glancing flatness of the steel plates after being pre-straightened is not more than 2 mm/1000 mm; and the temperature difference between the steel plates and the plates is not more than 8 DEG C after the roller way is used for varying the deceleration and the acceleration, and changing a starting mode.