The invention relates to a high-speed railway track foundation settlement monitoring system comprising a master monitoring terminal and multiple sub-monitoring terminals which are respectively arranged on all monitoring points of a track. Each sub-monitoring terminal respectively comprises a controller, and a satellite positioning module, an inertia measurement module and a sub-communication module which are respectively connected with the controller. The master monitoring terminal comprises a monitoring server and a master communication module which are interconnected. The master monitoring terminal is communicated with all the sub-monitoring terminals via the master communication module and the sub-communication modules. The invention also relates to a monitoring method based on the high-speed railway track foundation settlement monitoring system. Position information of monitoring points is acquired in real time on the basis of a conventional satellite measurement method in coordination with the inertia measurement module so that accuracy of high-speed railway track foundation settlement monitoring is effectively ensured.