AC operation with multiple full cycles has been successfullyperformed on the superconducting tokamak HT-7. In the experiment, itwas discovered that the saturation of the transformer magnetic fluxwith DEF, a signal name, was one of key aspects that affected the ACoperation. The conditions of DEF were examined through the DEFfeedback control system. By controlling the working patterns of thesubsystems, namely the poloidal field control system and densitycontrol system, it was guaranteed that DEF wouldremain in the non-saturated status.