This paper proposed a novel broadband filter using multi-layer sub-wavelength high-contrast grating (HCG) structure. This filter has wide bandwidth and good sideband suppression. We simulated and analyzed the effects of different numbers of layers and different grating indexes on filtering performance of the broadband filter. According to the simulated results, we designed a multilayer HCG broadband filter, which has bandwidth of 843 nm and center wavelength of 1550 nm.