The slow light propagation in a Ge20Sb15Se65 chalcogenide photonic crystal slab waveguide (PCSW) of air holes is investigated via the three-dimensional plane wave expansion (PWE) method. By perturbing the first two rows of air holes adjacent to the waveguide core, the group index, the bandwidth and the dispersion can be tuned effectively, and the symmetric chalcogenide photonic crystal slab waveguides with zero dispersion are obtained. The slow lights with the group indices of 125, 40, and 18 are demonstrated, with the bandwidths of 1.7, 5.6 and 9.7 nm, respectively. Finally, the effects of refractive index of chalcogenide materials on the slow light in the photonic crystal slab waveguide are discussed. It shows perfect slow-light properties in chalcogenide PCSWs and can be used as an affordable reference for further research in chalcogenide photonic crystal waveguide devices.