Aiming at the characteristics of high order and strong coupling of current source inverter （CSI） ultra high speed motor drive system， an improved decoupling control strategy based on stator current feedback active damping is proposed. Firstly， by constructing the equivalent model of CSI super high speed motor second-order system considering control delay in Z domain， a hierarchical decoupling drive system consisting of complex vector decoupling current outer loop and feedforward decoupling voltage inner loop is designed. Secondly， the stability of the three closed loop control system in the full speed domain is analyzed based on the reconstructed model， and the correlation between the instability of the decoupling strategy and the resonance problem of the second order system under high-speed conditions is discussed. Therefore， the stator current feedback active damping is introduced into the current loop regulator in this paper to solve the high order system resonance problem and realize the high performance and stable operation of the ultra high speed motor in the full speed domain. Finally， a CSI drive platform of 550 000 （r·min^-1）/110 W ultra high speed permanent magnet synchronous motor is built， and relevant simulations and experiments are carried out to verify the effectiveness and superiority of the proposed improvement strategy.