Abstract: More elements, more channels, system complexity and weak signal were the main difficulties in implementing 3D imaging by 2D array. The elements planning was designed, then the behavior of the time-space signal through discrete finite long window was analyzed and the rules to design probe was concluded. A square 2D array with 8×8 elements was designed based on computer simulation. 3D imaging was implemented by the array. Experiment showed that, testing system and the 2D array both had good performance. 3D imaging supplied information about contour of the defect.