In this work, we computationally designed a set of nitroxide diradical base pairs (rC+:rC) to propose promising magnetic building blocks for spintronic or magnetic molecular materials. C+:C12 is found to possess a considerably large antiferromagnetic-like (AFM-like) spin-coupling magnitude (J = -3286.681 cm-1) and sensitive magnetic responses to the external electric field. Especially, the presence of the Y direction field that is oriented perpendicular to intermolecular hydrogen bonds has the greatest influence on the magnetic exchange interaction (J being from -2549.578 to -4231.286 cm-1, ΔJY = 1681.708 cm-1), which could be understood by two simultaneously occurring effects. On the one hand, the external electric field in the -Y direction can regulate the charge polarization of negative and positive electrostatic potentials on C12 moiety and further facilitate the spin transport property. On the other hand, with increasing electric field strength on the -Y axis, the spin density on diradical sources diminishes and that on the coupler increases, which can lead to a homogenous spin-density distribution. The achieved understanding provides a new strategy for designing self-assembly magnetic nanomaterials or nanodevices and enhancing the AFM coupling through the assistance of external electric field.