Torsion mode and longitudinal mode are used primarily in ultrasonic guided wave inspection, especially L (0, 2) mode and T (0, 1) mode. There are some differences between them, like excitation method, mode of particle vibration, inspection ability and impact factor. So, it is very important to select the appropriate mode between L (0,2) and T(0,1). In this paper, the detection ability of two guided wave modes are compared and analyzed with regard to four aspects in the pipe: fluid, liquid level, defects, the angle between defect and wave propagation direction. The experimental results show that L (0,2) mode is more suitable for defect detection in pressure pipe than T (0,1) mode, but L (0,2) mode is more sensitive to fluid in a pipe. This paper provides a basis for selecting the mode of guided waves in ultrasonic detection.