Open source software USES software defect tracking system, which can effectively manage the related information of software defects, and build software defect data warehouse in the form of defect report. The severity attribute of software defect report can determine the important indicators such as the repairers, solving time and repairing rate of software defect. Much research on software defects focuses on severity analysis. In order to evaluate the work in the field of severity analysis, this paper reviews the existing studies. In particular, this paper introduces the main methods of severity study, and expounds the statistical characteristics analysis of severity attribute in software defect report data set. According to the research status, the research of severity analysis is divided into qualitative analysis and quantitative analysis, and analyzed in detail. At the same time, each part is empirically analyzed based on data from the Mozilla project and Eclipse project datasets. On this basis, this paper summarizes the existing work of severity analysis of defect report, and points out some possible problems in the work.