Abstract: Described here in the paper is the research that leads to having developed a wall thickness control system on the basis of the Python PyQt5 framework. A software platform for off-line process parameter adjustment of the mandrel pipe mill is set up by means of systematically analyzing the process of the mandrel pipe mill to extract the key process parameters as affecting the pipe wall thickness. The core of the said system covers the aspects including establishing a complete mathematical model of the mandrel mill process which involves such critical parameters as the wall reduction rate,the pass parameters,the speed and rpm,etc.;developing a prediction and adjustment module for the wall thickness reduction rate. The system is verified via the actual application to a 3-roll,6-stand FQM as located at a certain domestic tube plant,showing that the predicted result is well in compliance with the actually measured data. The said control system as newly developed provides a reliable wall thickness control solution for production of the continuously-rolled pipe,and lays the technical foundation for the follow-up intelligence upgrade.