The bus plays an important role in serving the urban travel demand in both developed and developing countries. Unfortunately, the heavy operation of this mode may come together with crashes, which may cause adverse effects on its image and service quality from the view of the public, thereby leading to a reduction in ridership. The knowledge on characteristics of crashes is, therefore, desired. While most of the research focus is on the probability of crash occurrence, the severity of crashes has recently attracted increasing attention from researchers. This paper aims to synthesize previous studies on crash severity. By means of looking at 11 studies carefully selected from the SCOPUS database, this paper has provided a detailed synthesis of data collection, research areas, used samples, seven factor groups associated with the crash severity (Temporal characteristics, Location and infrastructure characteristics, Service and vehicle characteristics, Traffic characteristics, Crash characteristics, Weather characteristics, Driver characteristics and behaviours), and analytical methods. Afterwards, research gaps and shortcomings of the existing research are highlighted for proposing future research directions. This review could help to save efforts to obtain a clear understanding of bus crash severity. It may be an informative reference for those newly accessing the field of bus crash severity and/or intending to develop solutions to this problem.