Abstract: On the base of beam controlled theory, ultrasonic phased array focusing testing was simulated by the software CIVA. By changing the number of stimulated elements, frequency and depth of focusing, the relationship among those was analyzed. The method of real testing in focusing mode and non-focusing mode was discussed with the result of manual defect testing. Study shows, that there exists area of superposition and separation to focal point and maximum acoustic pressure in focusing mode. The best effective area of focusing should be within the near field of ultrasound. In non-focusing mode, the number of elements stimulated should be chosen according to the depth of defect.