Abstract: In the hot strip steel continuous rolling process， when rolling suspended or roll changed， the thickness of the following strip steel was out of the precise control level which affected the yield of the strip. To solve the problem， the roll wear model and thermal expansion model were proposed， and the steady state error was put into the models to improve the spring equation. Practical application results showed that the first piece strip steel of the thickness deviation within 40μm range after changing rolls was up to 90%， and the thickness accuracy reached within 30μm under different rolling intervals， which met the requirement of the automatic gauge control system and improve the product yield. The generic solution of the steady state error in the spring equation was provided. The proposed model was online used properly for a long time， and it was suitable for the industrial production.

Key words: model calculation, thickness precision, roll wear, thermal expansion, static error