The invention discloses an iron core stacking method, in particular to a full bias-seam iron core stepping stacking method, belonging to the field of manufacture of transformer components. The full bias seam iron core stepping stacking method comprises the following steps: N grades of iron core units are sequentially stacked on a stacking platform; a first-grade iron core unit positioned in the middle of all N grades of iron core units is the maximal grade iron core unit; each grade of iron core unit comprises at least one group of silicon steel sheets; each group of silicon steel sheets is formed by stacking a plurality of layers of silicon steel sheet; each layer of silicon steel sheets comprises a center post, a left post, a right post, an upper yoke and a lower yoke, wherein the center post is positioned in the middle; the left post is positioned at the left side of the center post; the right post is positioned at the right side of the center post; the upper yoke is positioned at the first end of the center post, and the lower yoke is positioned at the second end of the center post. The invention can lead a magnetic flow to pass through a joint step by step, thereby ensuring that the magnetic flow more regularly flows at both sides of the joint, preventing a plurality of joint air gaps from concentrating in the same part and reducing the local consumption of the iron core in the joint position; and the invention provides the full bias-seam stepping stacking method which can reduce the no-load consumption and the noise of the iron core.