Abstract: Aiming at the problem that the accurate rack rolled thickness was not available from the spring equation in the traditional automatic gauge control AGC system which was limited by the accuracy of mill stiffness coefficient and the linear conditions of the spring curve， a method based on the mill stretch characteristic curve was proposed to calculate the strip thickness， and then the new feed forward AGC， gaugemeter AGC and the correlation models between the gaugemeter AGC and monitor AGC were put forward. The optimized AGC system was applied successfully in a hot strip mill， and the practical application showed that the thickness of the strip steels with the specification of 35mm was controlled within the allowable thickness deviation of ±20μm， and the thickness precision validation rate reached over 962%， which satisfied the requirement of production site control.

Key words: hot strip mills, mill stretch characteristic curves, feedforward AGC, monitor AGC, thickness gauge AGC