Systemetical and full studies on the issue of small-signal angular stability featured by low-frequency power oscillation in power system for over half a century have greatly pushed forward the development of mordern power system. The progress of studies on low-frequency power oscillations of power system are reviewed according to the timeline. Firstly, the discovery of hunting phenomenon of synchronous generators and its solution in earlier time are recalled. Then the theory and experiment researches of low-frequency power oscillations for simple single machine infinite systems are concluded. Secondly, by introducing the theories and methods on damping control and analysis of low-frequency power oscillations, model analysis and damping torque analysis applied to low-frequency power oscillations are reviewed and discussed. Finally, recent research progress on the impact of large-scale wind power integration on power system small-signal angular stability is reviewed.