Abstract: The correct calculation of flow resistance of single-phase flow in undulating vibration state has significant influence on the safety of floating nuclear power plant. The influence of different undulating vibration conditions and flow conditions on the single-phase water friction pressure drop in the inclined pipe passage was studied experimentally. The results show that the vibration friction pressure drop is larger than that in steady state, and fluctuates periodically. The average value of vibration frictional resistance coefficient decreases with the increase of Reynolds number and the angle of pipe, increases first and then decreases with the increase of pipe diameter and vibration frequency, and increases with amplitude of vibration. The empirical formula for calculating the vibration frictional resistance coefficient of single-phase flow in the inclined pipe under undulating vibration was obtained by fitting the experimental data. The calculated results agree well with the experimental results. It provides a new way to calculate the flow resistance of undulating vibration single-phase water.