Abstract: To address the problems of dead-time effect, parameter perturbation, and limited communication resources in permanent magnet synchronous motor (PMSM) control, an error-coupled dead-time disturbance observation method based on Caputo fractional-order derivative and its composite control strategy is proposed. By utilizing the memory characteristics of the Caputo derivative, the historical dependence and gradient tracking capability for time-varying dead-time disturbances are enhanced, thereby improving the accuracy of disturbance estimation and the speed of dynamic response. On the one hand, an extended state observer capable of accurately estimating the equivalent dead-time disturbance is designed to realize the integration of dead-time compensation and state observation. On the other hand, combined with time-varying state constraints and an event-triggered mechanism, the communication resource consumption is reduced while ensuring system stability. Finally, the effectiveness and applicability of the proposed method are verified through numerical simulations.