This paper studies the functions of overstep chemistry calculation oxygen δ in high Tc copper oxide superconductors and analyzes the relative experiments' results. It is believed that the function of overstep chemistry calculation oxygen in Y series high Tc copper oxide superconductors is to adjust the change of effective electric charge P on the [Cu-O] p link or [Cu-O] P plane and this affects the bonding intensity on the CuO 2 plane, which in turn, adjusts the Y series high oxide superconductor's Tc.