The discrete POD method is used to analyze the rotating flow to further understand and accurately model the details of the flow physics in this paper. The low-order flow modes are obtained using modified discrete POD method proposed by Sirovich, and are used for the reconstruction of the unsteady flow field. The unsteady rotational flow of a simplified impeller is used as numerical example to show the effectiveness of the POD method for the analysis of rotating flow. The numerical results show that the maximal reconstruction deviation is reduced to a very low level with a small increase in the number of low order modes. Furthermore, the regions at relatively high values of deviation shrink distinctly to impeller tip nearby in more accurate approximations.