Abstract: A numerical model of a low-head pump turbine has been developed to study its characteristics of pressure fluctuations using a realizable k-ε turbulence model, focusing on full-passage simulations of the unsteady flows for four guide vane opening conditions, i.e., a0=29mm, 33mm, 37mm, and 41mm. Pressure signals at four sampling points were compared with experimental measurements. The results show that this turbulence model has a good overall performance and its accuracy is better in the cases of larger openings. Generally, pressure fluctuations tend to be weaker at larger openings, and pressure signals at the opening of 29mm show the strongest fluctuations of the four openings. Because the rotating wheel causes a rotor-stator interaction in the flow passage from the guide vanes through the runner to the draft tube, pressure fluctuations are periodic at the sampling points in the two vaneless spaces: the section between the guide vanes and runner, and the cone section of draft tube. The dominant frequencies of these time variations are equal to the frequency of blade passing through, and at the sampling points in the cone section a peak value appears on the amplitude-frequency curves. Due to the vortex strip in draft tube, the dominant frequencies at the sampling points in bent pipe are 0.17~0.56 times of the frequency of runner passing through.