One suggests to modify pass design to improve efficiency of hexagon bar steel rolling via improvement of rolling process stability, as well as, to improve quality of products via increasing accuracy of finishing profile. Preliminary pass design is made in the form of edge hexagon with 1.12-1.25 ratio of height to width by incision in rolls. It is suggested to make bottom of every pass designs in the form of the bell by second order curve. Formula describing this curve is given. Pass designs of this circuit which are used to obtain 75 mm size hexagon, are shown. Application of modified system of pass designs at rolling of 62, 65 and 75 mm size hexagon steel product lots has determined the following advantages: efficiency is increased by 8-10%, manual and metal consumption to produce rolls are reduced by 50%, roll wear is reduced by 10-15% and spoilage value is reduced, as well.