Abstract: Cs,RbNa₂KSb photocathode of make used of improvement technique preparation, higher- sensitiveness, lesser- thermal emission and better reprodueibility etc, response litht of green- to- infrared portion of the spectrum in particularly was improved. Strcture model of energy bands of surface Cs,RbNa₂KSb phtocathode was be down for discussion, to the result of experiment was satisfied with explain.