A new sensor with piezoelectric ceramic is designed for Structural Health Monitoring on high voltage transmission cable used for exciting elastic wave on the surface of transmission cable to obtain the propagation characteristics. Based on an experimental setup with two transducers, a signal generator and a data acquisition system, the dispersive curve of guided wave in the transmission cable is measured through Gabor wavelet transform. The results show that there are at least four modes above 30 kHz, but there are only two modes below 30 kHz, which is suitable for the research of SHM. Another experiment for the damping of elastic wave on the transmission cable is carried out. The curve of the relationship between amplitude attenuation and propagating distance is achieved. The influence of frequency on peak value is researched. Results show that the wave attenuation is exponential function.