According to the equivalent relation between the substrate integrated waveguide and conventional rectangular waveguide, a compact wideband fourway equal filter power divider is designed based on substrate integrated waveguide(SIW).The design uses coaxial feed in the center. SIWtomicrostrip transitions are used for the output ports with equal amplitude and phase . The fourrow metal holes are used to divide the waveguide into four cavities on average. In the passband,there are three modes (TE101/TE202/TE303) in the cavities, which can realize trimode bandpass. The high order mode(TE202) is suppressed by the perturbation of the inductive hole, and the stop band performance is improved. Measured results of the filter power divider have shown that the bandwidth is more than 2.5 GHz at centre frequency of 10 GHz. The fourway filter power divider has the advantages of small size, simple manufacture, easy integration with other circuits, etc.