A surfactant-assisted colloidal chemistry technique for the controllable growth of various PbS architectural nanostructures catalyzed by Ag nanocrystal seeds was reported. The sizes and morphologies of the obtained PbS nanostructures were dependent on the amount of Ag nanocrystal seeds and the ratio of Pb to S precursors. By varying the amount of Ag seed, sphere-, cube- and rod-shaped PbS nanostructures were obtained; while the morphologies changed from nano-scaled sphere to small cube and then to large truncated-cube when decreasing the precursors' ratio of Pb to S from 5:1 to 2:1 and then to 1:2 with the fixation of the amount of Ag seed. Control of morphology under different conditions has been systematically studied and the mechanism of morphology formation was also primarily discussed.