Magnetic tunnel junction with a large tunneling magnetoresistance has attracted great attention due to its importance in the spintronics applications. By performing extensive density functional theory calculations combined with the nonequilibrium Green's function method, we examine the spin-dependent transport properties of a magnetic tunnel junction, in which a non-polar SrTiO3 barrier layer is sandwiched between two Heusler alloy Co2MnSi electrodes. Theoretical results clearly reveal that the near perfect spin-filtering effect appears in the parallel magnetization configuration (PC). The transmission coefficient in the PC at the Fermi level is several orders of magnitude larger than that of in the antiparallel magnetization configuration, resulting in a huge tunneling magnetoresistance (i.e. >10^6), which originates from the coherent spin-polarized tunneling, due to the half-metallic nature of Co2MnSi electrode and the significant spin-polarization of the interfacial Ti 3d orbital.