Roll pass design is one of the important content of making the rolling technology of section steel.The traditional pass design relies mainly on artificial experience,which brings some tedious calculation and great consumption of raw materials.In order to improve production efficiency,the constitute and the design methods of the roll system for thread-steel-bar are analyzed during stretching,further rolling and finished rolling.The mathematical models and the(experience) formulas used for the roll design in the past are revised.The computer aided roll design system is developed for thread-steelbar based on the structural means of compiling program.The authors adopt Visual Basic6.0 as a visual program tool,and combine the basic design theory of the thread-steel-bar's roll and the practical experience.The system can shorten the design cycle of the new product development,and reduce the energy consumption of the rolling mill and the distribution of production.