The invention discloses a dimensional uniformity compensation method and device based on casting molds. The dimensional uniformity compensation method and device based on the casting molds are mainlyapplied to the field of robot automatic polishing of castings. The method comprises the following steps that the casting molds are numbered, a polishing path is sectioned according to portions to be polished, parts cast by the different casting molds are chosen to be polished, and compensation values are determined according to the polishing effect; and when workpieces are grabbed, the position ofa piston of an air cylinder is acquired through a position sensor, the number of the mold of the current part is calculated by a PLC according to the simulation quantity of the position of the pistonand transmitted to a robot, and the robot calls the corresponding compensation value to conduct polishing. The dimensional uniformity compensation method and device based on the casting molds can compensate for the errors, caused by the dimensional uniformity errors of the casting molds, of the castings, the polishing accuracy and the polishing effect are improved, and the machining errors causedby the dimensional errors of the casting molds are avoided.