Abstract: In order to study the transmitting characteristics of ultrasonic guided wave in pipe and select the guided wave mode suitable for non-destructive testing(NDT), the authors analyse, on the basis of elastic dynamics theory, the characteristics of multimode and dispersion of guided wave transmitted in pipe. They calculate, through programming numeric value, the dispersion curve of guided wave and the displacement distribution of various mode of the wave along the wall of pipe. The calculated result of numeric value and Fourier decomposition method are used to simulate the transmitting of guided wave in pipe so that the time domain waveform of different mode of wave after transmitting a certain distance is obtained. The results show that at special frequency, L(0, 2) mode is the ideal mode of pipe defects NDT for less dispersion and fast transmitting of guided wave. Numeric simulation is consistent with theoretical analysis, and proves that the Fourier decomposition method can effectively simulate the transmitting characteristics of ultrasonic guided wave in pipe.