One compact model of drain current valid in the subthreshold region, for short-channel cylindrical gate-all-around metal-oxide-semiconductor field-effect transistors including the source-to-drain tunneling has been proposed. From a two-dimensional analysis, the drain-induced barrier lowering effect is modeled according to our previous work. In this paper, by introducing the profile of the energy subband level along the electron transport direction into the Wentzel-Kramers-Brillouin approximation, we can numerically derive the expression of the tunneling transmission coefficients. Then, the source-to-drain tunneling current in the subthreshold region is evaluated by using the Landauer formula. The results obtained are compared with non-equilibrium Green's function transport simulations with a good accuracy.