Recently the manufacturing method for slabs in steel mills is shifting from the rolling to continuous casting. On the other hand, the increase of yield in hot rolling mills calls for an improvement of the accuracy of strip width along the entire length. Therefore, in the near future, new width control system that consists of heavy duty edging mills and automatic width control edging mills should be developed. This paper describes basic problems and characteristics of edge rolling, mainly by caliber roll, on the basis of the results of experimental tests using 1/10 scale plasticine slabs, and verifies these data by theoretical analysis to investigate the width control system of hot strip mills.