We report a robust method by which colloidal PbS nanosheets can be synthesized with nearly 100% success rate. It is achieved by replacing the lead acetate by lead oxide for preparation of the lead precursor. Acetic acid either injected externally or produced during the reaction can significantly affect the growth of the nanosheets. The existence of water in the reaction solution makes the nanosheets smaller in lateral size while the purity of trioctylphosphine has no significant effect on the nanosheet growth.