The discharge structure in an electronegative Ar/SF6 inductively coupled plasma is investigated in the article at low pressure, 10mTorr. Parabola profile in the electronegative plasma core is given by the fluid simulation, in accordance to the prediction of analytical theory. Except the ordinary sheath, the overall discharge is separated into the electronegative core and electropositive edge, which are connected by a dielectric-type double layer. This is a novel type of double layer, distinct from the previously reported ones that are found in the space plasma and triggered by stream instability. A self-coagulated density bump is observed stamping onto the parabolic basis at the chamber periphery along polar direction. In the core, the anion is obeyed to the Boltzmann’s balance and the density profile of electron is flattened at its own and the anion Boltzmann balances. The discovered discharge structure in electronegative plasma by means of simulation and theory is important for people to better understand and utilize the laboratory plasmas