Mth-band filters are an important class of digital filters and are often used in multirate digital signal processing systems, filter banks and wavelets. This paper considers the design problem of the maxflat R-regular IIR Mth-band filters with arbitrarily specified group delays, and gives a new closed- form expression for its filter coefficients. The filter coefficients are directly derived by solving a linear system of Van-dermonde equations, which are obtained from the regularity condition of the maxflat R-regular Mth-band filters via the blockwise waveform moments. Finally, some examples are designed to demonstrate the effectiveness of the proposed maxflat R-regular IIR Mth-band filters.