Abstract: To study the characteristics of side-coupled photonic crystal filter, the coupled mode theory (CMT) and the transfer matrix method (TMM) were used to analyze the dependence of the filter-s reflection spectrum on the period of resonator, the value Q, and the number of cavities. The simulation result showed that the reflection spectrum was symmetrical when the phase shift was n/2, the bandwidth of reflection spectrum peak decreased as Q increased, and the bandwidth of reflection spectrum peak increased and the side lobe occurred at the same time as N increased. To overcome the increasing side lobe due to the increase of bandwidth, the chirp and cascade technology similar to one-dimensional photonic crystal filter was used to achieve sidelobe suppression. This work can be used for the design of the photonic crystal filter.