We present a theoretical study of spin transport through a magnetic C-28 molecule sandwiched between two Au (111) electrodes. The ab initio modeling is performed by spin density functional theory and non-equilibrium Green's function technique. The results clearly show that the spin-resolved transmission spectra of C-28 molecular junctions exhibit robust transport spin polarization (TSP) characteristics, which depends on the contact configuration. At the small bias voltage, the conductance of C-28 is mainly determined by the spin-down electrons. The TSP behavior can be effectively tuned by the gate. Our results indicate that C-28 molecule holds promise in future molecular spintronics applications. (C) 2012 Elsevier B. V. All rights reserved.