PbS nanostructures with different morphologies, such as rod-like, belt-like, downy-velvet-flower-like and dendrite-like, were fabricated successfully under varied reaction conditions in aqueous solution at lower temperature by the assistance of surfactant CTAB. Especially, among all the synthesis methods for PbS nanocrystals, this is the first report using basic acetate of lead, which was formed at initial reaction stage, as a precursor to control the crystal nucleation rate. This synthesis method is a promising one to metal sulfide for its easy control, low-cost and large-scale production. X-ray powder diffraction (XRD), transmission electron microscopy (TEM), selected area electron diffraction (SAED), field-emission scanning electron microscopy (FE-SEM) and UV-visible spectrophotometer (UV-vis) were used to characterize the products. A rational mechanism is proposed and three control factors to the crystal directional growth are also concluded.