obtaining a PCB raw data and a preset accuracy requirement, wherein the PCB raw data comprises an actual expansion length, a theoretical expansion length, a raw preshrinking design length, an actual expansion length, a quantity of gold fingers, a width of the gold fingers, a distance between the gold fingers, and a preshrinking design value;

determining a preshrinking compensation value according to the PCB raw data and the preset accuracy requirement;

determining a PCB unit distance expansion dimension according to the raw preshrinking design length, the actual expansion length and the quantity of the gold fingers;

determining a symmetrical quantity of the gold fingers according to the PCB unit distance expansion dimension and the preshrinking compensation value;

determining the first sectional length according to the width of the gold fingers, the distance between the gold fingers, and the symmetrical quantity of the gold fingers;

determining a preshrinking compensation ratio according to the preshrinking compensation value and the first sectional length, wherein the preshrinking compensation ratio is one-half of quotient of the preshrinking compensation value and the first sectional length;

determining a first preshrinking design ratio according to the preshrinking design value and the preshrinking compensation ratio;

determining a first section ideal expansion length according to the first sectional length and the first preshrinking design ratio;

determining a second section ideal expansion length according to the theoretical expansion length and the first ideal expansion length;

determining a second sectional length according to the preshrinking design value and the second section ideal expansion length; and

determining an optimization preshrinking design length according to the first sectional length and the second sectional length.