An uniform silicon waveguide is proposed featuring ultralow-dispersion slow light. The core of the waveguide consists of one silicon trip and two pairs of air/silicon strip and the cladding is composed of several alternative silicon and air strips, which form a transverse band gap to confine propagating light in the core. The waveguide has several nearly linear photonic bands in a large frequency range, which can support broadband slow modes with a group velocity of 0.03–0.08c and tolerable group velocity dispersion.