Abstract: The paper introduced a forecasting system of deformation of the earth’s surface in three-underground mining for forecasting subsidence and deformation of the earth’s surface caused by mining of arbitrary shape working face, which integrated visualization data input, data management, data processing and visualization output together. It briefly introduced composition and functions of the system, and described calculation model, arithmetic realization, methods of input and output of data of the system. At last,it gave an application example of the system. The example showed that the calculation and forecasting of the system was accurate and reliable, the functions of the system achieved the design requirement.