The effect of external magnetic field on the spin evolution of the radical pair (RP) generated from photo-induced electron transfer from skatole to 2,4,6-triphenyl pyrilium tetrafluoroborate in aqueous SDS micellar medium has been investigated. The yield of escape radicals gradually increases with increasing field and ultimately reaches saturation. The yield of escaped radicals at saturating fields is almost four times the corresponding zero-field value. At low fields the magnetic field dependence of the escape yield is ascribed to HFI-Zeeman competition and at relatively higher fields, to the relaxation mechanism induced by anisotropic HFI [delta(hfi)]. A saturation in MFE is observed at high fields, which is a consequence of the competition between the spin-rephasing process and the fast escape process,