Abstract: Battery safety has seriously affected the popularity and promotion of electric vehicles. In recent years, battery fire incidents of electric vehicles have occurred frequently, arousing great social concern. The main safety accidents of electric vehicles in the past five years are analyzed in this papery. The distribution and development of the causes of the electric vehicle fire events over the years are summarized. The characteristics of battery failures behind the major accident causes and their mechanism of triggering the thermal runaway are discussed. The main research teams in battery safety issues, including the overcharge, external short circuit, internal short circuit, over-discharge, and the extrusion collision, are reviewed. The main research results and shortcomings of the existing publications are discussed. Finally, the research trends and ideas of battery safety and thermal runaway diagnosis and early warning are discussed.