Virtual machining simulation is becoming a must-have or an important tool currently in traditional machining process. With it, a series of trial machining can be avoided. However, the situation is different for high-energy-beam cutting. Till now, there is no accurate virtual cutting simulation tool which could simulate the physical cutting process accurately. As a soft knife, whose shape is changing dynamically, it is a big challenge to accurately define the tool shape and build an accurate 3D geometrical model as a virtual model for simulation. Aiming at abrasive water jet (AWJ) machining, a new method to build a soft knife profile based on energy distribution analysis has been explored in this paper. Through 3D point cloud data of kerf profile, a 3D model of the abrasive water jet profile has been built under different working conditions. To evaluate the effectiveness of the self-defined tool shape, the compensation strategy based on 3D AWJ profile has been carried out in the actual cutting process. The results show that 3D AWJ profile is beneficial to improve the machining accuracy. And this method can be extended to other high-energy-beam cutting tools such as laser and plasma.