Abstract: For the sake of risk assessments of centimeter/millimeter-level space debris impac-ting satellites,a vulnerability analysis method has been developed to estimate the system failure probability PK/H of satellite with different damage degree.The proposed method is constructed on the basis of Failure Mode and Effect Analysis (FMEA ),combined with Shot-line method and failure tree method.In this paper,the main idea and each key technique of this vulnerability anal-ysis method in detail were introduced and an application example was presented in the end.This method can be applied for manned space missions also,which is significant for risk assessments of aircrafts and shielding structure design optimization.