The sulfur-doped Y-junction carbon nanotubes (S-YCNTs) were prepared by chemical vapor deposition of carbon disulfide using Fe as catalyst. Sulfur can be incorporated into the nanotubes with an identifiable amount, forming sulfur-doped carbon nanotubes. The growth of asymmetrical Y-branches in the nanotubes may be related to the presence of sulfur from precursor. The structure and morphology of S-YCNTs can be controlled by processing parameters. The S-YCNTs were characterized by SEM, TEM, EDX, and XPS, respectively. The growth mechanism of S-YCNTs was discussed in terms of the role of sulfur from carbon feedstock.