Abstract: Based on modularization, this paper proposes the 4-layer model of GD102 motion controller's driver through research on its characteristics. The four layers are kernel layer, register layer, basic command layer, and application layer. This paper analyses the function and implementation method of each layer. The communications between layers are also referred to. The driver of the motion controller is developed by the tool of DriverWorks through analyzing the composition of the kernel mode driver and the processing of the IRP in Windows2000. Some key problems during processing of program development are discussed in this paper. The driver has been applied in an open numerical control system successfully.