Models of the position and tool forces of backhoe hydraulic excavator were built based on the full analysis of kinematics, kinetic performance of working device and mathematic model of tool forces. Various restrictive factors of tool forces, which appeared in the work process, were discussed. A computation program based on VB 6.0 was compiled, which was used to calculate tool forces in any position of the working area. Computer plotting of drawing mine map that was divided by restricting factors was realized. The experimental results demonstrated the feasibility of this method.