The theoretical model of quantum efficiency of the reflective varied doping GaAs photocathode is proposed, which adopts the weighted mean method based on the quantum efficiency formula of exponential doping and uniform doping photocathode. By this model the quantum efficiency curves of a reflective GaAs photocathode under varied doping structure have been fit and we obtained the precise best fit in different incident photon wavebands. The phenomena that the contributions of doping structures to the cathode quantum efficiency are different was discovered. This phenomena has been analysed and discussed detailedly in the paper.