Abstract: According to the different characteristic of the different period planar electromagnetic band-gap (EBG) structures and the equivalent circuit model of the planar EBG structure, a novel multi-period planar EBG structure is proposed.The simulation results show that stop-band is from 0.7GHz to 8.4GHz and the bandwidth is 7.7GHz at-30dB.Compared with the traditional large-period planar EBG structure and the small one, the bandwidth increases by 2.2GHz and 1.2 GHz respectively.Moreover, the simulation results show that this novel EBG structure can be used to inhibit the simultaneous switching noise (SSN) effectively and it gives a novel method to broaden the bandwidth of planar EBG structures.Finally, signal integrity is well achieved by the time-domain simulation.