In order to avoid the low sensitivity common problem of 532nm sensitive narrow-band response photocathode, variable doping narrow-band response GaAlAs photocathode structure is designed. The photocathode is composed of GaAs substrates, Ga1-x1Alx1As buffer layer, Ga1-x2Alx2As doping concentration gradient emissive layer and GaAs protection layer from bottom to top. Among them, exponential doping method is applied to Ga1-x2Alx2As unit layer from the bottom to the top. And a preparation methods of GaAlAs photocathode is developed. For the GaAlAs photocathode components which grow well, chemical cleaning, heating purification and (Cs, O) activation are operated, and ultimately Cs / O activation layer is formed on the surface of Ga1-x2Alx2As doping concentration gradient emissive layer. The highest sensitivity of the photocathode peak response is at 532nm, and the photocathode quantum efficiency in 532nm peaks at 36%.