Abstract: The non-integer dimension ultrasonic phased array and its scanning and testing methods in acoustic logging are studied.At first,the focusing acoustic field excited by a 1.25D,1.5D,and 1.75D phased arrays is analyzed,and the imaging resolution in the elevation direction and the reduction of dynamic elements are investigated.Then,the focusing and deflexion characteristics of the acoustical fields excited by the annular and segmented annular phased arrays are studied and compared with 2D surface array.The application method of 1.25D,1.5D,1.75D,annular and segmented annular phased arrays in acoustic logging is analyzed and discussed.It provides a theoretical foundation for application of the ultrasonic phased array in acoustic logging.