Abstract: Rotating stall is an important instability phenomenon of rotating fluid machinery (e.g. pump turbine). This paper presents a review of the rotating stall of pump turbines operating in generating mode, focusing on the primary characteristics of such instability and the corresponding pressure wave transmission. We discuss the basic concept, generation conditions, physical mechanisms, and development/transmission of a rotating stall cell in pump turbines, and summarize the methods for identification of rotating stall, including data analysis based on pressure fluctuation measurements and experiments of bubble injection and tuft visualization. To explore the influence of rotating stall on the operation of pump turbines, two important issues are suggested for the future research on rotating stall in pump turbines.