The　effects　of　defects　on　the　performance　of　all　inorganic　perovskite　solar　cells　was　studied　using　a　one-dimensional　solar　cell　simulation　software　SCAPS.　It　is　found　that　in　the　device　ITO/SnO2/CsPbI3/CuI/Au，the　density　of　the　defects　at　the　CuI/CsPbI3　interface　and　in　the　CsPbI3　photoactive　layer　has　dramatically　influence　on　the　performance　of　the　device.　With　the　increase　of　the　defect　density，the　open-circuit　voltage，short-circuit　current，filling　factor，and　power　conversion　efficiency　of　the　device　all　decrease，especially　when　the　defect　density　exceeds　1015　cm-3.　On　the　contrary，the　defects　at　the　CsPbI3/SnO2　interface　have　almost　no　effect　on　device　performance.　By　optimizing　the　defect　density　of　the　device，the　thickness　and　doping　concentration　of　the　photoactive　layer，a　power　conversion　efficiency　higher　than　20%　can　be　obtained　in　the　all　inorganic　perovskite　solar　cells.　©　2023　Chines　Academy　of　Sciences.　All　rights　reserved.