A three-dimensional finite-element simulation of stretching technological parameters of heavy forgings is performed by using ANSYS program. The law of intal stress distribution with different bt/h (tool width ratio) and different bb/h (blank width ratio) is studied. Consequently, the critical tool width ratio( bt/h )cr and blank width ratio( bb/h )cr leading no bi-axial tension are obtained. It lays a credible foundation for designing reasonable stretching technology.