The edge crack behavior of copper foil in asymmetrical micro-rolling was studied. The effects of the speed ratio between rolls, grain size and stress state in the deformation zone on edge cracks of the rolled piece in asymmetrical rolling were analyzed. Low plasticity, uneven deformation and longitudinal secondary tensile stress generated in the edge area of the rolled piece during the rolling process are the main causes of edge cracks. The larger the grain size of the rolled piece, the smaller the number of edge cracks and the deeper the expansion depth, and the larger the spacing between cracks under the same rolling reduction. Asymmetrical rolling can effectively increase the rolling reduction at when the copper foil fist shows edge cracks compared to symmetrical rolling. This enhancement is attributed to the shearing stress induced by asymmetrical rolling, which reduces the rolling force and longitudinal secondary tensile stress, and increases the residual compressive stress on the surface of the rolled piece. The edge crack defects of copper foil can be effectively reduced by increasing the speed ratio between the rolls in asymmetrical rolling.