In the plain mining area with a high ground-water table in eastern China, with the rapid development of coal industry. Especially when the fully-mechanized top-coal caving mining is adopted, the great surface deformation is resulted. Meanwhile, a great amount of groundwater is being extracted, which causes the leveling control network lose its functions quickly. In order to maintain the safe production, it is a fundamental measure for providing reliable datum to construct a scientific deformation monitoring system. In this paper, the theory and method of high precision deformation monitoring system with GPS geodetic technique in about 1000km2 mining area are studied. And it focuses on the scheme of deformation monitoring system with GPS in dynamic deforming area, the index system of data quality control, and data analysis model. Finally a case about deformation monitoring is introduced and some discussions are included.