With the development of technology, more and more products begin to use free form surfaces. Since abrasive water jet has unique and efficient cutting ability and the ability to handle complex shapes, it has gradually attracted attention in the low cost and efficient treatment of high-performance parts. In order to improve machining efficiency and reduce machining allowance when abrasive water jet is machining complex surfaces, a new method of motion simulation of abrasive water jet path is studied in this paper, combining with the theory of curve and surface fitting in computer graphics. Specifically, the continuous B-spline curve is used to describe the profile shape of abrasive water jet cutting material. According to the tensor product principle and a new parameterization method, the product model surface is decomposed into multiple curves. Subsequently, the water jet path simulation is realized by combining the optimization algorithm. The problem of water jet path planning is transformed into two B-spline curve position approximation problems. Finally, the method proposed in this paper is applied to blade disc machining to verify its effectiveness. Compared with existing methods, the method proposed in this paper has a higher removal rate.