Based on the ultrahigh vacuum interconnection setup for photocathode preparation and surface analysis, the activation experiments were performed on reflective GaAs photocathodes, and the microarea analysis of the photocathodes after chemical cleaning and Cs/O activation was implemented by the scanning focused Xray photoelectron spectroscopy. Micro regions of interest were located to be detected with the aid of the Xray beam induced secondary electron image, and the impurities on the surface were analyzed more accurately. It is found that the GaAs cathode samples after chemical cleaning would suffer from secondary contamination by the metal sheet, accompanied by a small amount of sodium and cesium. Surface analysis and activation experiments show that high temperature heating and Cs/O activation can not remove the sodium contamination, which can affect the desorption of arsenic on the surface, hinder the adsorption of Cs and O in the activation process, and finally reduce the photoemission performance of the activated cathode. The scanning focused Xray imaging technology is used to analyze the microarea of cathode surface, which would assist in investigating the change of surface composition before and after cathode activation more accurately.