The enhancement effect of the phase conjugation wave was studied,which was produced by a third order nonlinear optical medium(NLM) in a(AB)~N(D)~2(BA)~N Bragg microcavity made of one-dimensional photonic crystals.The gain factor of the phase conjugation wave was derived out when the resonance condition was satisfied for incident optical wave and the Bragg microcavity mode.Because of stronger resonance enhancement to incident pump beam given by the Bragg microcavity,the enhancement effect of the phase conjugation wave produced by Bragg microcavity was more outstanding than that caused by naked third order NLM.The theoretical analysis and numerical calculation showed the Bragg microcavity with larger number N of periods identified with a Fabry-Perot(F-P) cavity when the resonance condition was satisfied for incident optical wave and the Bragg microcavity mode.