We have studied the spontaneous emission from a three-level atom with an external-driving field in a photonic crystal. As a result of quantum interference and photon localization, the population in the two upper levels displays quasi-oscillatory or oscillatory behavior. This depends on the initial atomic state and the relative positions of the two upper levels from the forbidden gap. The intensity and the phase of the external field can affect spontaneous emission from the atom. The properties are different from a three-level atom either in vacuum or in a photonic crystal without an external driving field.