The invention provides an earthquake monitoring early-warning system and an earthquake monitoring early-warning method. The system comprises an Internet of Things constellation, a ground center, a ground terminal and an earthquake monitoring early-warning platform, wherein the Internet of Things constellation consists of a plurality of Internet of Things satellites; the ground terminal is used foracquiring crustal movement data detected by an earthquake monitoring device and used for transmitting acquired data to the Internet of Things satellites; the Internet of Things satellites are used for receiving data transmitted from the ground terminal, used for storing data, and used for transmitting data to the ground center when being moved above the ground center; the ground center is used for receiving data transmitted from the Internet of Things satellites, used for analyzing and processing the data, and used for transmitting the data to the earthquake monitoring early-warning platform;the earthquake monitoring early-warning platform is used for receiving the data, and used for judging an earthquake risk and/or implementing earthquake magnitude prediction on the basis of the data and prestored earthquake criterions. By adopting the system and the method provided by the invention, data acquisition and transmission are carried out through the Internet of Things constellation, remote-distance real-time monitoring and early warning of earthquake can be achieved, and active effects that ground network covering and operator guard are not needed are achieved.