In order to solve the coupling vibration problem of the fan impeller during rotation, the centrifugal fan impeller was taken as the research object, κ-ε turbulence model and vibration mechanics theory were used to analyze the flow field and mode around the impeller, and the distributions of the pressure and velocity in the internal flow field of the centrifugal fan under different rotating speed were obtained. The results show that the large compression area is distributed around the fan outlet, the center speed of the impeller is small, and the radial speed increases gradually; with the increase of the rotating speed, the first four modes of the impeller decrease gradually, and the last two modes increase gradually. The conclusion provides a reference for the working condition and optimal design of the fan impeller.