Abstract: This Paper outlines a general software system of computer aided design for roll forging aiies, realizing the automation of the whole process from design calculation to draughting , of the roll forging. For any hot forgings to be made by the rollging technogy, as long as the initial data used to describe the forging geometry and other indispensable parameters are input, the computer can complete whole design job from the process design to the die size calculation quickly and exactly. A combination method which uses three kinds of volumetric modes, the isometric section model, the varying secton model, and the axisymmetric model, is suggested for the geometric description of forgings. Therefore only relatively few input data are needed to describe different forging shapes. A new mathematical model is presented for automatical simplification of mass distribution diagrams, so that the design efficiency can be raised, obviously.