Provided is a composition for controlling pluripotency of stem cells including an LIN28A methylation inhibitor and a screening method of the LIN28A methylation inhibitor, and more particularly, a composition for controlling pluripotency of stem cells including an inhibitor controlling methylation of 135th lysine of LIN28A that is methylated by SET7/9, or a composition for treating cancer, and a screening method of the inhibitor, wherein the screening method includes (a) contacting a candidate material with a cell, the cell having a gene introduced thereinto; (b) measuring a methylation level of the 135th lysine of the LIN28A; and (c) selecting an inhibitor controlling methylation of the 135th lysine of the LIN28A. That is, the present invention relates to a composition for controlling pluripotency of embryonic stem cells, or an anti-cancer composition, and a screening method of the inhibitor. The method of the present invention is possible to screen materials capable of controlling pluripotency of embryonic stem cells or materials having anti-cancer activity, and the materials screened by the method of the present invention may control pluripotency of embryonic stem cells and inhibit growth of cancer cells, which is effective for disorders of stem cell differentiation or preparation of cancer therapeutic agents.