Abstract: An effective method is presented to implement virtual control and simulation of robot motion in a threedimensional (3D) space in VC (visual C) platform. An open architecture is constructed, which is capable of directly importing and embedding other programs written in C-language, importing robot 3D-solid models generated using SolidWorks, Pro/E, etc. and saving them in a binary-tree-data-structure based simulation model container for the convenient and quick search. Robot kinematic models can be derived based on defined D-H (Denavit-Hartenberg) parameters, and real-time analysis, computation, virtual control and simulation of robot motion can be performed according to a specified path in Windows-based, IntervalZero RTX® supported VC platform. By introducing the Observer Pattern in Computer Design Pattern, a real-time information updating mechanism among various software modules is established in the simulation system to effectively avoid the impact of of Windows' non-real-time data transmission in nature upon the real-time requirements imposed by the simulation system. The friction stir welding (FSW) robot being developed is used as an example to illustrate details about the construction of 3D robot models and their data structures for access, system information communication protocols, and 3D simulation of robot motion based on a given path. A virtual welding process using a simulation-generated robot end-effector trajectory as the tool-end welding path is demonstrated, which shows the effectiveness of the open-architecture, virtual 3D motion control and simulation system.