A design method of signal source for exciting ultrasonic guided wave in the pipe was presented, for reducing the adverse effects of dispersive phenomena in pipeline ultrasonic guided wave inspection, using ultra-high-speed microcontroller DS89C430, digital-analog converter(DAC) device AD9708, operational amplifier(OP) LM318 and other devices, a narrow-band signal generator which can generate single acoustic frequency signal modulated by Hanning window is deugned, the generator is devoted to excite ultrasonic guided wave, both the width of Hanning window and the frequency of single acoustic frequency signal are adjustable. Results show that the design is reasonable, the frequency of single acoustic frequency and the cycles’s number of the single acoustic frequency modulated by Hanning window are all adjustable easily.