The invention provides an implementing method of cloud numerical control system. The method implements a numerical control system with functions of online error compensation, CAD/CAPP/CAM/CNC integrating and interactively cooperative assembling machining control. The cloud numerical control system includes a small cloud numerical control system a large cloud numerical control system. The small cloud numerical control system focuses on inside control of a single numerical control machining device and includes a cloud control core node, cloud measure and control subnodes and fine-tuning driving units. The large cloud numerical control system is based on the small cloud numerical control system and performs interactively cooperative machining between multiple numerical control machining devices for different workpieces to be assembled.