Abstract: Numerical simulation of longitudinal crack detection in pipes using ultrasonic guided waves T(0,1) mode was made.A valid finite element model with longitudinally oriented through-thickness crack of various length was given,on which T(0,1)mode ultrasonic guided wave was excited.The results of numerical simu- lation showed the relation between longitudinal length and reflection coefficient which was defined as the am- plitude of the reflected signal divided by the amplitude of the incident signal as well as the circumferential distribution of reflected signal amplitude.Method to determine location of longitudinal and circumferentially locating crack using T(0,1)mode ultrasonic guided waves was also introduced.Simulation results show that T(0,1)mode is sensitive to longitudinal crack detection and the circumferential position where maximal reflection is received is the same with the circumferential position of longitudinal crack,as a whole,the reflection coefficient shows an increasing-decreasing tendency.