The high-speed linear induction motor (LIM) has multiple parameters coupling and fast time-varying characteristics, which easily leads to current and thrust control instability and further restricts speed improvement. To address this issue, this paper proposes a decoupling mathematical modelling method to accurately characterize the time-varying parameter feature of LIMs. Subsequently, an indirect magnetic field orientation control strategy, consisting of the voltage feedforward control algorithm and a PID feedback control algorithm with time-varying parameters, is proposed based on the mathematical model. The simulation results demonstrate that the proposed method exhibits better stability in the fast changes of parameters, and the speed of the LIM is superior to the traditional methods.