Abstract: The traditional single variable PID control method cannot meet the requirements of the pre-mill grinding system which is a pure delay and strong coupling multivariable system. To meet the production requirements of the grain size and low energy consumption,a diagonal transfer function of matrix was designed by considering the effects of various factors of the grinding system. The transfer function matrix was obtained through having the diagonalisation of transfer function of a system model that contained an uncertainty of time-delay link,whose lagging model was approximated by the first-order Pade model according to the ratio of time delay and time constant,and then it was regarded as internal model control model for designing a IMC-PID controller,in which the control system added was performed step response comparative simulation with conventional PID control system. The results show that the IMC-PID control system with decoupling link has strong robustness and satisfactory regulation quality,which can effectively solve the problem of coupling and time lag between the grinding system output,and has a better dynamic performance and robustness ability,which have a good engineering application value.