This paper briefly reviews the development process of earthquake early warning and introduces the basic principles of earthquake early warning as well as the main determination methods for key parameters such as earthquake location，early warning magnitude and predicted intensity. As an effective means to mitigate earthquake disasters，earthquake early warning systems have been set up in many countries and regions of the world. Taking the system construction and application effectiveness as the breakthrough point，this paper introduces the main earthquake early warning systems in the world and the related progress in China. And then，based on the main challenges faced by the earthquake early warning，new and potentially innovative technologies and methods for future earthquake early warning system are prospected from the aspects of sensors，signal processing algorithms and networking modes.