We analysis the radial equations for massive Dirac fields in Schwarzschild black hole spacetimes. Different approximation formulae under the WKB scheme are developed for the transmission probability T of the radial wavefunction with E 2 ≫V m , E 2 ≈V m , and E 2 ≪V m , where E is the energy of the field and V m is the maximum value of the effective potential. Explicit results of T in these approximations are given for various values of E , the mass m , and the angular momentum parameter κ of the fields. We also discuss the dependence of T on these parameters.