Roof insulators of high-speed electric multiple units (EMUS) are important mechanical supporting component for high voltage equipment, which in addition isolates the catenary from the train’s roof in electric, the flashover of roof insulators may lead to interruption of power supply or even outage. However, due to the specificity and severity of operation environment for high-speed railway in China, accidents caused by the flashover of insulators often occurred, which seriously affect the safe operation of high-speed railway. Through deep research on revelant scientific problems, accidents of trains result from insulator flashover have been greatly reduced, but these kinds of problem haven’t been solved fundamentally. In this paper, research progresses of roof insulators used for high-speed EMUS are reviewed from the follwing aspects: structure and material property, pollution flashover characteristics, sand dust flashover characteristics under strong wind, insulation online monitoring, methods for accelerated aging test and aging test platform. In the end, this paper forcasts future research key points.