Abstract: Owing to the demand of the data sharing between different application programs, based on the feature of Windows NT and VC++, a method for data sharing by using DLL is proposed. The method solves the problem of data sharing of multitasking on real-time dynamic simulation environment for Windows NT. The shared data are defined in one DLL file and which can be shared by every application program, even the application program with different languages. The application program can also access the shared data indirectly. The method is convenient and useful.