Abstract: Abstract: Pipeline is a carrier of cascade pumping station with long distance water conveyance. Therefore, it is particularly important to keep the stable operation of pipeline structure. In order to ensure the safe operation of pipeline structure, it is significant to research the main influence factors of pipeline vibration and the contributions of different factors to pipeline structure. Based on prototype observation data, vibration source compositions and their influences on pipeline structure were investigated through analyzing the power spectral density of vibration data. Taking the No.2 pipeline of Pumping Station 3 in Jindian River pumping irrigation as the research object, six points were set up in different parts of pipeline. Three vibration sensors were placed in each measuring point, from which vibration data were collected in three directions of pipeline. First of all, on the basis of mathematical statistics theory and the observation data of vibration sensors, vibration frequencies of pipeline structure excited by four and five units in the process of normal operation and switch machine were identified according to the spectrum analysis. Dominant frequencies of pipeline structure were counted under different working conditions to determine the dynamic load sources and to introduce the vibration source compositions of pipeline structure. Furthermore, the contributions of different frequencies were calculated when the vibrations of main points reached the maximum values under different working conditions. At the same time, the contributions of the measured frequency bands energy to the whole vibration response were calculated. The analysis results showed that, under the working condition of steady operation of units, the contribution of vibration energy caused by blade frequency and rotation frequency was 73.4%, and the contribution of low frequency water-flow pulsation was about 12%. During unit start-up, the vibration energy contribution of low frequency water-flow pulsation was increased to 33.7%, and the contribution of blade frequency still was about 40%. During unit shutdown, compared with the steady operation conditions, the vibration energy contributions of low frequency and high frequency induced by water-pipeline coupling were increased by 73.3% and 21.7%, respectively. The study showed that the vibration of blade frequency and rotation frequency were the main vibration sources when the unit was stable in operation. The vibration of blade frequency and low frequency water-flow were the main vibration resources during unit start-up. The low frequency water-flow and high frequency induced by water-pipeline coupling were the main vibration resources during unit shutdown, and low frequency water-flow had greater effect on pipeline vibration along the direction of flow. The research results can be used for evaluating the sources of pipeline vibration and the contributions of different frequencies. This study provides a scientific basis for the safe operation and active control of pipeline structure.