Abstract: The equilibrium configuration and magnetic distribution were achieved by numerically solving Grad-Shafranov equation when the total current exceeded zero in the AC operation experiment on CT-6B. Considering the motion equation of particles in magnetic field, trajectories of deuterium ions in this equilibrium configuration were simulated, and also, the ratios and positions of deuterium ions loss were statistically calculated. The results indicate that the equilibrium configuration is the current-reversal equilibrium configurations with two oppositely flowing current components on the high-field side and low-field side when the total current exceeds zero, magnetic islands exist at high-field side and low-field side both, and current value is extreme value near the magnetic island. The particles in high-field side lose barely, but loss happens when radial location is much high at low-field side and the loss rate increases as it reaches to boundary. Basically, positions of loss locate beneath equatorial plane and loss reaches the extreme value at the very bottom. Trajectory of deuterium ions converts from passing particle trajectory to lost particle trajectory firstly, and further, to trapped particle trajectory when the initial angle becomes large.