We examine 1) photocurrent from Cs3Sb photocathode as a function of anode voltage below 200 V, 2) relationship between quantum efficiency for photoemission and fabrication condition by “sandwich method”, 3) recovery of photoemission by an additional Cs deposition and 4) effect of surface protection of Cs3Sb photocathode by WO3 and Cr2O3 film in the passive state. It was ascertained that deposition of 1 to 3-atomic-layer W or Cr film elongated lifetime of the photoemission after they became WO3 or Cr2O3 in passive state due to oxidation.