Abstract: The improved confinement phase was observed during modulating toroidal current on the Hefei superconducting Tokamak7 (HT7 ). This improved plasma confinement phase is characterized by suppressing magnetohydrodynamic (MHD) instabilities effectively thus increased the central line averaged electron density and the central electron temperature about 33%, output steeper density profiles, and reduced hydrogen radiation from the edge as well. The global energy confinement time was increased by 27%~45%; The impurity radiation was reduced by modulation of plasma toroidal current; Particle confinement time was increased about two times; A more strong radial negative electric field formed inside the limiter. The radial electric field during modulating current was calculated and disscussed.