Based on the model of tension variation in transmission line, the paper calculates the change in the horizontal component and the vertical component and develops online monitoring system of transmission line galloping. Based on conductor structure, the pressure sensor adapted to line measurement is designed. The system exports digital signal of tension variation through A/D transformation. Based on ZigBee wireless transmission technology, the function of tension variation is realized. Finally through certain comparison test of transmission line, it is proved that the measurement system can effectively implement the transmission line galloping. When the wind speed is greater than 6.7 m/s, the galloping.amplitude of conductor is positively correlated with the wind speed. When the wind speed is 12 m/s, it reaches a maximum of 6.1 m. As the wind speed increases, the amplitude of the wire is oscillating.