In order to control low frequency noise, a two-dimensional plate-connected phononic crystal was designed. The dispersion curve and displacement field of the structure were calculated by finite element method. The results show that the designed structure has a band gap between 29.37 Hz and 354.07 Hz. Compared with the model in the literature, this structure has a lower initial frequency and a wider band gap, which indicates that it is more accessible to obtain low frequency band gap in phononic crystals with connecting plate structure. The enlarged band gap was also explained by vibration modal analysis of displacement field and mass spring model. On this basis, the influences of the width of the connecting plate and the opening radius of the silicon rubber coating on the band gap were further discussed. It is noted that as the width of the connecting plate decreases, the band gap can be increased gradually. As the pore radius tapped in the silicon rubber coating decreases, the band gap further increases.