Abstract.A two-phase four-pole air-core compulsator is designed and its basic electromagnetic characteristics are analyzed. The absence of specific compensation components simplifies the compulsator structure design and increases the reliability and pulse current versatility. A new self-excitation circuit structure is proposed for two-phase compulsator, which can improve the excitation efficiency and reduce the excitation loss. The experimental results show that the 5g projectile can be accelerated to approximately 2km/s. simultaneously, the effect of series inductance in waveform regulation is verified.