In this letter, a novel miniaturized low-pass filter (LPF) is designed on the proposed substrate integrated suspended line (SISL) double-layer metasubstrates platform. In order to achieve the miniaturization of the LPF by SISL technology, we designed double-layer II-shaped metasubstrates, which show high effective permittivity of greater than 9. Compared with the LPF on SISL without metasubstrate, the designed LPF on SISL double-layer metasubstrates shows some good characteristics, containing miniaturized structure of 0.0055 λg × 0.0113 λg × 0.0022 λg with a size reduction of 84.9%, low loss of less than 0.37 dB, and self-packaging advantage.