Abstract: To master the law of ground deformation in the goaf is the prerequisite and foundation for scientific prevention and control of ground collapse, and also an important monitoring content for the dynamic change of the geological environment of the mine. With Jinfeng coal mine in Ningdong coal base as a study case and on the basis of collecting and understanding the mining time, mining depth, mining coal thickness, length of working face, width of working face and direction of working face, the authors set up the automatic GPS monitoring point on the surface of the working face of Jinfeng coal mine. The mining process is unified with the time and space of ground deformation. The authors tried to study the law of ground deformation time and deformation under mining and similar mining conditions. The result shows that the ground deformation of 011202 working face was usually subjected to severe deformation about 13 months after mining and reached the stability 15-17 months after the beginning of deformation, with the maximum cumulative variable being about 3300mm. The ground deformation in the goaf of 011805 working face usually occurred violently 10-11 months after mining and reached the stability 13-16 months after the beginning of deformation, with the maximum cumulative variable being about 2600mm. The research results provide quantitative basis for the prevention of surface subsidence and the prevention and treatment of gob collapse under similar mining conditions.