The invention discloses a method and a system for decision making and early warning based on ground subsidence monitoring. The method comprises the following steps of setting a plurality of monitoring points, and positioning the monitoring points in a monitoring map, so as to obtain the monitoring data; calculating and analyzing the monitoring data, so as to obtain the feature values of the monitoring data; establishing a single measuring point calculating model, a multi-measuring point calculating model and a time sequence model; determining the parameters of the models, so as to obtain a single measuring point predicting model, a multi-measuring point predicting model and a time sequence predicting model; generating a subsidence hazard level judging rule; obtaining the to-be-monitored data, and calculating the subsidence amount or subsidence rate of each model; determining the ground subsidence hazard level of a monitoring point on the basis of the subsidence amount or subsidence rate of each model according to the subsidence hazard level judging rule, and performing early warning. The system comprises a monitoring point positioning module, a data obtaining module, a data analysis module and a display module. The method and the system have the advantages that the monitoring, decision making and early warning on the ground subsidence are performed, and the integrated data management and processing are realized.