As an important IV-VI semiconductor, PbS has attracted considerable attention due to its special small direct band-gap energy (0.41eV) and a large exciton Bohr radius (18 nm), which permit quantum size confinement effect to be clearly evident even for relatively larger particles or crystallites. Due to its distinguished properties, the control of the size and morphology of PbS nanocrystals has been a primary subject. Various methods have been used for the preparation of low-dimensional PbS nanostructures. Among them, hydrothermal method has been widely used to prepare low-dimensional PbS nanostructure due to its simpleness, high-efficiency, low-cost, and more practice. Previously, PbS nanostructures have been prepared by hydrothermal method in the presence of surfactant or solvothermal method. However, The control of size and morphology of PbS nanocrystals is difficult and complicated. Herein, we report a thioglyeolic acid (TGA) assisted hydrothermal method to control the morphology of PbS nanocrystals. Star-shaped, rod-like and cubic-shaped PbS nanocrystals have been obtained by TGA-assisted hydrothermal process using different sulphur and lead source. X-ray diffraction (XRD) reveals that the PbS nanocrystals are of the cubic rock-salt structure and well crystallized. Transmission electron microscopy (TEM) and scanning electron microscopy (SEM) observations show that the morphology of PbS nanocrystals is easily controlled according to sulphur, lead source, and pH value. Furthermore, the mechanism and the critical role of the TGA-assisted hydrothermal synthesis on PbS nanostructures have been preliminary presented.