Having the advantages of no motion elements, high reliability, undemanding maintenance and good medium flexibility, the swirl meter has been widely used to measure the gas, liquid and steam in chemical, petroleum as well as processing industries. For the current one-piezoelectricpressure-sensor swirl meter, however, the measuring error caused by the interference pressure oscillation limits its application in the system where pressure is unsteady, or a noisemaker is nearby. In this paper, the fluid dynamic features inside the channel of the swirl meter are studied numerically and by experiment. The time dependent vortex motions as well as the hydrodynamic vibrations within the channel of the swirl meter are simulated using the CFD approaches of the RNG k-e model. The computed flow fields indicate that the eccentric motion of vortexes initiates an axisymmetric pressure oscillation within the vortex precession area of the swirl meter. The frequency of the oscillation shifts linearly with volume flow rates. Both the calculated and the measured results prove that the hydrodynamic vibrations on the arbitrary axisymmetric points are equal in amplitude and frequency but with a 180 degree phase difference. By installing differential pressure transducers on such the axisymmetric points, the signals of the vortex pressure oscillations are enhanced, while the interferential signals are suppressed, enabling the antiinterference performance and low-flowrate sensibility of the swirmeter to be effectively improved.