In this paper, the resistor effect on isolation bandwidth of a compact Wilkinson power divider is studied. The discussion is based on an equal modified compact power divider on RO4003, with center frequency of 2.4 GHz. In this compact power divider, stepped impedance interdigital coupling sections were introduced to replace the quarter wavelength impedance transformer of Wilkinson power divider to realize the bandpass filtering capability. The theoretical analysis, simulation and measurement results are also discussed in this paper.