Abstract: In order to improve stability and reliability of the profile gauge system and to fit the harsh on-line environment better, the gas ionization chamber was used as detector of the profile gauge. In this article, the characteristic of the ionization chamber was analyzed and the structure of the chamber was studied and designed. The feature of ‘dual-array’ was discussed and the arrangement mode of the array was studied. The dual-array gas ionization chamber detector designed eventually meets the requirements of the profile gauge and increases the resolution and reconstruction precision of the system.