Heavy forgings are the essential parts of some nuclear, electrical power generation, rolling mill equipments. Based on the experimental results, one thermo-mechanica1 coupled finite element model was developed to study the effects of forging processing parameters, including the deformation degree, tool width ratio, and blank width ratio, on the axial effective strain during stretching process of heavy forgings. Results show that: (1) The effective strain around the central point rapidly increases as the deformation degree was increased. When the deformation degree is larger than 15%, there are little changes of the effective strain along the deformed block centerline. (2) The effective strain in central point increases and then decreases with the increase of tool width ratio, and the critical tool width ratio is 0.8, which is valid for most stretching processes. (3) The effective strain increases with the increase of initial blank width ratio, and the effects of blank width ratio on the effective strain in axial centerline are most obvious near the central point.