Numerical control system is the core technology for flexible manufacturing system and computer integrated manufacturing system. In this paper, we fully take advantage of the surface reconstruction technology to optimize tool path planning, and then promote the performance of numerical control system. The main idea of this paper is to utilize the Non-uniform rational Basis spline (NURBS) in numerical control system, which is a powerful mathematical model to describe curves and surfaces based on computer graphics. Next, we provide a novel tool path planning algorithm for numerical control system based on NURBS curve through three steps: 1) constructing the NURBS curve node vector, 2) NURBS curve interpolation, 3) Optimizing fitting control points by NURBS curve fitting. Finally, experimental results demonstrate that fitting precision is greatly enhanced and numerical control program is also significantly simplified by NURBS curve fitting.