The invention provides a novel nanostructure photocathode which comprises a patterned catalytic layer, a patterned vertical carbon nanotube formed on the catalytic layer and a metal nanoparticle witha plasmon effect modified on the vertical carbon nanotube. The invention further provides a preparation method of the novel nanostructure photocathode. The novel nanostructure photocathode and the preparation method provided by the invention have the benefits that an electrostatic shielding effect on the cathode surface can be effectively prevented through the patterning treatment of a cathode electron emission material, and a fringe effect is fully utilized, so that a cathode surface barrier is compressed, and a threshold of light energy required for electron emission is lowered; the carbon nanotube and the metal nanoparticle are combined, so that the excellent electrical performance and the environmental stability of the carbon nanotube are utilized, and meanwhile, a surface plasmon resonance effect of the metal nanoparticle is also utilized. Therefore, the enhancement of a light wave local electric field and the photon absorption enhancement can be realized.