[en] Highlights: • MeC3Me molecule has spin filtration effect. • MeC3Me molecule has negative differential resistance. • MeC3Me molecule has abnormally magnetoelectric effect. Based on non-equilibrium Green's function and density functional theory, a first-principles study of the spin-polarized transport properties and magnetism of 1,3-dimethylpropynylidene molecule sandwiched in two Ag electrodes is performed. Strong spin-polarized negative differential resistance and spin filtration effect are present. We also find that the net spin moments of molecular magnet abnormally decrease driven by electric field because the molecular orbitals around Fermi level have opposite spin direction and that non-spin-polarized electrical read out of spin states for single molecular magnets is possible.