Abstract: When the traditional 20-high rolling mill is used to expand the ultra-thin specifications during the rolling of silicon steel, the evaluation of equipment capacity and the selection of process parameters are based on experience and field trials. The lack of theoretical support leads to a high risk of equipment damage and high trial and error costs. At the same time, the product quality cannot be guaranteed after the specification expansion. In response to the above problems, fully considering the equipment and process characteristics of the 20-high rolling mill, combined with actual rolling data on site, and taking into account rolling stability and strip surface defect control, a 20-high rolling mill rolling capability evaluation model and technology was established and corresponding rolling ability accounting software was developed. This software can be used to accurately calculate rolling capacity of a 20-high rolling mill for silicon steel. It was applied to a cold rolling plant for silicon steel of a steel company. Through comparative analysis of the calculated minimum product thickness and the actual export product thickness, it was found that, under the premise of ensuring hourly output and considering rolling stability and defect control capabilities, the calculated minimum product thickness is smaller than the actual product thickness, and the product thickness specification has room for expansion in a thinner direction, which laid a theoretical foundation for the subsequent product quality control and rolling process development of high-grade non-oriented silicon steel and oriented silicon steel to expand to thinner specifications.