In this paper, ignition characteristics in deuterium-tritium(D-T) and D-{sup 3}He tokamak reactors with spin-polarized fuels are presented by using the ignition access condition based on the generalized saddle point in the representation of ({bar P}{sub ht}{tau}{sup 2}{sub E}, n{tau}{sub E}, T). Enhancement of the D-T fusion cross section due to parallel spin polarization with respect to the magnetic field can reduce the confinement enhancement factor required for reaching ignition by {approximately} 20% if fusion particle loss is not induced by the anisotropic fusion particle distribution. Spin polarization is this effective when a D-T reactor is marginal for ignition. In D-{sup 3}He fusion, it is more advantageous to use spin-polarized fuel in the heating phase than in the case of D-T fusion. The auxiliary heating power to reach ignition, which is rather large for D-{sup 3}He fusion, can be reduced by a factor of 2 to 3 compared with the unpolarized case. The deuterium-deuterium fusion suppression effect, it is exists, does not alter the ignition condition much. Various problems related to the spin polarization scheme are also discussed.