The invention provides a once fine blanking forming method for a thick plate disc. The method comprises the following steps of: 1) preparation of equipment, raw materials and upper and lower once fine blanking forming dies; and 2) once fine blanking forming. The step 2) comprises the following steps that: 1, the upper and lower once fine blanking forming dies are arranged on an upper tabletop and a lower tabletop of a fine blanking machine respectively, and when a fine blanking mold is at an opening position, a bar stock is fed to a fine blanking station; (2) the fine blanking machine is started, and a lower workbench of the fine blanking machine moves upwards to apply blanking force FS to a female die, a round hole male die and an irregularly-shaped hole male die, apply blank holding force FR to a dowel bar, a round knock-out pin and an irregularly-shaped knock-out pin and apply back pressure FG to the knock-out pins; and 3, a lower workbench of the fine blanking machine moves downwards, a pressure plate withdraws the cut bar stock from a punch die under the action of the blank holding force FR, and a pushing plate ejects a thick plate disc part from the female die under the action of the back pressure FG to obtain the formed thick plate disc part. The method is applied to batch production, and has the characteristics of operational simplicity, high efficiency, cost saving and stable quality.